On a Monday afternoon last spring, at a diner in Manhattan, Tina Fey recalled her first days on the job at "Saturday Night Live." She told me, "I'd had my eye on the show forever, the way other kids have their eye on Derek Jeter." As we were talking, a man in his twenties, with wild tufts of dark hair, stopped by our table, which was near the soda fountain. Over the roar of a blender, he shouted to Fey, "Can I tell you that you are amazing? I don't want to interrupt, but you are truly, truly amazing!" Fey thanked him, staring down at her plate. When her admirer retreated, she grinned. "Most of the time you're too busy to think about it," she told me. "But every now and then you say, 'I work at "Saturday Night Live," and that is so cool.'"

Fey joined the show six years ago, when Lorne Michaels, the creator and executive producer, summoned her from Chicago, where she was working at Second City, the comedy troupe. After twenty years on the air, "S.N.L." had suffered several seasons of declining ratings. Fey was known as a versatile performer with a broad range and a gift for satire, but Michaels wanted her to write for the show.

She started work in an office on the seventeenth floor of 30 Rockefeller Plaza, NBC's headquarters, which offered a view of the Empire State Building. She missed Chicago, but "S.N.L."'s backstage dynamics inspired her. "In that comfort zone, we say the meanest kind of things," she explained. "If you want to make an audience laugh, you dress a man up like an old lady and push her down the stairs. If you want to make comedy writers laugh, you push an actual old lady down the stairs." In 1999, Michaels invited Fey to become a head writer, and the following year she began performing in sketches and on "Weekend Update."

In addition to being the first woman to hold the title of head writer at "S.N.L.," Fey is also the first female performer to become the face of a show that other female comics, including the original cast members Jane Curtin and Laraine Newman, have cited for frat-house hoo-ha. Janeane Garofalo, who was briefly on the show in the mid-nineties (during what she described in the "S.N.L." oral history, "Live from New York," as "the year of fag-bashing and using the words 'bitch' and 'whore' in a sketch"), calls the current period "the Tina Fey regime," and its reforms impress her. "I'm assuming somebody has come in and done an exorcism," she says. Audiences and critics have responded well to Fey's influence. In 2001, Fey and the writing team won a Writers Guild Award for "Saturday Night Live: The 25th Anniversary Special." Last year, the show won an Emmy for outstanding writing, its first in that category since 1989. And this season "S.N.L." is once again attracting more viewers than any other late-night show, including the "Tonight Show" with Jay Leno and "Late Show with David Letterman."

Fey began performing on the show after Michaels saw her onstage in a sketch that she had put together with Rachel Dratch, an "S.N.L." performer, at the Upright Citizens Brigade Theatre, in Chelsea, and proposed that she audition to co-anchor "Weekend Update" with Jimmy Fallon. Unlike Fey, Fallon-a boisterous, clownish figure-had started out as a standup comic, but they got along well, and viewers liked their priss-and-goof routine. On a Saturday afternoon last spring, Fey, Fallon, and Michael Shoemaker, one of the show's producers, along with the writers Doug Abeles, Charlie Grandy, and Michael Schur, who produces "Update," milled around a table in a conference room, as they do every Saturday afternoon of the television season, for a meeting they refer to as "bagel times." The writers "call down the jokes," reading through a dozen topical one-liners to be delivered during the three-minute segment. "Bagel times" is their last opportunity to convene before the dress rehearsal that precedes the live broadcast, which that week featured Salma Hayek as the host and Christina Aguilera as the musical guest. "Update" is always the last element of the show that the writers work on, and, except for the "feature" interludes, in which guests stop by the news desk-that night Hayek appeared as a buxom sidekick to a Latino showman-Fey and Fallon don't formally rehearse.

The writers were trying to come up with a joke about the Dixie Chicks, whose lead singer had slighted President Bush. Doug Abeles read the setup: "While in London on Thursday, the Dixie Chicks angered country-music fans when lead singer Natalie Maines told the audience, 'Just so you know, we're ashamed that the President of the United States is from Texas.'" Fey squinted, as if detecting a quip in the distance. She is slight, with bright eyes, fine features, and thick brown hair. A white scar runs up her left cheek. (She has had the scar since childhood but she hates to discuss it.) Wearing a shabby green cardigan, Levi's, and sneakers, she was eating a bagel out of which she had scooped most of the soft bread. "We apologize," she suddenly declared. "We forgot that our entire fan base were hillbillies and idiots." Everyone chuckled except Shoemaker, who pointed out that Dixie Chicks fans were people like his wife. Fey agreed, without apology, and the group moved on to a joke about a man who swallowed a diamond ring in order to ask his proctologist to marry him.

Fey peered at a monitor that showed performers rehearsing the night's routines in a studio downstairs. Hayek was swooning in a mock Mexican soap opera. Fey grimaced. "That sketch is in peril," she said. A premise for another joke came up. A summer camp in northern Virginia trains preteen girls to be models, someone explained; they learn makeup, hair, and runway techniques. At the end of the summer, the writers proposed, the camp would donate the best little model to. . . someone. Tommy Lee? Kid Rock? Everyone looked stumped.

Fallon abruptly turned to me. "Name someone who dates supermodels," he commanded. Then he bellowed, "Give me five names! Give me five!"

"Rod Stewart?" I said.

No one laughed except Fey, who giggled happily.

"Do you really think that's funny?" Fallon asked, turning to her.

"Nah," she said. "I'm just trying to make her feel better."

The other writers and performers defer to Fey. "If she laughs, everyone's laughing," Fallon told me. Fey writes two comedy sketches each week, and runs one of two pivotal and often ego-bruising "rewrite tables" every Thursday. (Dennis McNicholas, the show's other head writer, runs the other table.) And she is one of a small group of writers and producers who decide which sketches will air, as well as which writers get to join the staff. During the past few seasons, Fey has seen to it that the female performers (Amy Poehler, Rachel Dratch, and Maya Rudolph) play recurring, center-stage parts. Poehler and Dratch also write prolifically, often in collaboration with the staff writers Emily Spivey and Paula Pell. (Only three of the show's twenty full-time writers are women, but two of them, Fey and Pell, have senior positions.) Dratch told me, "I love writing with Tina, but I'm always so self-conscious." Poehler said, "Tina likes to be at the top of the mountain, keeping an eye on things." And yet, at the read-through, at least in my presence, Fey was considerate and accessible. She solicited a range of opinions, paid earnest compliments, and showed political convictions about international law and the consequences of jingoism. (America's current troubles make Fey miss the previous Administration: "The Clinton years were the best of times," she told me. "Because there was a nonviolent, giant, sexy scandal. And I long for a return to those times every day.") Only every now and then did she turn to a writer and say something like "Jesus, how long did it take you to come up with that?"

Still searching for a punch line about the Dixie Chicks, Schur suggested that an analogy might work. Abeles, a friendly, lanky man in his late thirties, stepped up. "No one has alienated their fan base this much since Jenna Jameson stopped doing anal," he offered. People laughed politely, and someone hooted; everyone knew the line would stall at the department of Standards and Practices. Fey, who seemed to have momentarily lost interest, skimmed an article in the Post. (She gets most of her news from CNN and a packet of newspaper clips that the show's staff prepares for her.) Soon afterward, the meeting adjourned, and Fey headed downstairs to the run-through of the sketches. Schur appointed Abeles and Grandy to solve the Dixie Chicks puzzle by dress rehearsal. Later, no one could say who came up with the punch line, but at airtime it ran: "If you'd like to hear more of what Natalie Maines has to say, check out the new government wiretap on all of her phones." The audience seemed to like it.

Fey's first comedy job was as the anonymous author of a column in the Acorn, the Upper Darby, Pennsylvania, high-school newspaper. She was born in Upper Darby, a middle-class suburb of Philadelphia, in May, 1970, when it was home to many Greek- and Italian-Americans. Fey's mother is Greek-American and her father is German-Scottish, but she's wary of claiming an ethnic identity. "I've said a few things about being Greek, and now every Greek organization wants to adopt me," Fey told me. She admired her parents: her father for his integrity and his versatility (he has worked as a paramedic, a grant writer, and a mystery novelist) and her mother-a homemaker who spent her evenings playing poker-for her wit. She has one sibling, an older brother, Peter, who is a Web-site editor at QVC, the home-shopping network. As children, they did comedy routines together. Peter remembers a drawing that Tina made when she was about seven: it showed people walking down the street holding hands with wedges of Swiss cheese, and the caption read, "What a friend we have in cheeses!"

Fey wrote her high-school column as "the Colonel"-an acorn pun. She says that the column was "about school policy and teachers. I remember I got busted because I was trying to say that something would 'go down in the annals of history,' but it was a double-entendre with 'anal' and I didn't get away with it." Her sense of humor, however, didn't make her cool. Instead, she was a straight-A student who packed her schedule with extracurricular activities, including the newspaper and choir. She has a soft but precise singing voice.

High-school social dynamics still fascinate Fey, who has written a screenplay about teen-agers for Lorne Michaels' Broadway Video Motion Pictures, whose offices are at Paramount Pictures. Currently in production in Toronto (starring Lindsay Lohan and directed by Mark S. Waters, both of "Freaky Friday"), Fey's "Mean Girls" tells the story of a girl named Cady, who, having been home-schooled, enters her junior year in a public high school knowing nothing about cliques, makeup, dating, dieting, lying to her parents, or betraying her friends. She learns. The movie is based on a parenting book called "Queen Bees & Wannabes," by Rosalind Wiseman; Fey was impressed by Wiseman's characterization of girls' inhumanity to girls. "Girls are capable of spending a lot of time with someone and hating them," Fey explained to me.

This is a topic that she knows something about. "I was a mean girl," she told me, recalling that she used to ridicule wayward classmates, reserving particular scorn for kids who drank, cut school, overdressed, or slept around. She has a hard time explaining her motives-"It's a defense mechanism"-but her hostility persisted after she enrolled at the University of Virginia. "When I was eighteen or nineteen, that was all that I was, caustic," she says. She started out as an English major but switched to theatre and settled into the life of a "drama geek." On a campus renowned for keg parties, she refused to drink. In her second year, she remained in student housing, even though most of her classmates moved off campus; she preferred to be close to Culbreth, the university's theatre. "I used to do a monologue from a one-act play by Tennessee Williams called 'This Property Is Condemned,'" Fey told me. "And, I have to say, I was pretty good." In 1992, her last year of college, she played Sally Bowles in "Cabaret."

After graduation, Fey moved to Chicago; Second City's reputation as an improv Mecca had piqued her interest, because, as she told me, "I knew it was where a lot of 'S.N.L.' people had started." She hung around acting workshops and, at one point, held a job as the child-care registrar at the Y.M.C.A. before she was invited to join the troupe, in 1994. Her work was eclectic in form: monologues, sketches, one-acts. That same year, she met Jeff Richmond, a piano player at an improv school, who would later become her husband. Richmond is a levelheaded Ohioan, whose humor is more antic than cutting, and Fey believes that he is good for her character. Richmond described his first glimpse of Fey, whom he saw doing improv: "I don't want to say she was funny 'for a woman,' but there were so many talented men there at the time, and then suddenly there was Tina, who was so funny-and she was at home with all those boys on the stage." (Three years after Fey left Chicago, Richmond joined her in New York, where-on his own merits, the people at "S.N.L." take care to point out-he, too, was eventually hired by the show, to compose music for sketches.) In June of 1997, at the suggestion of Adam McKay, a former Second City player who was then the head writer at "S.N.L.," Fey sent some scripts to Lorne Michaels. In August, Michaels called her to New York. Though she had applied for the job, she had some qualms about taking it. She was twenty-seven, and she was finally doing what she loved: improvisational comedy, eight shows a week. She told Amy Poehler, whom she knew from the Chicago comedy scene, that she dreaded leaving Second City and moving away from Richmond. Poehler asked her how much money she would be making in New York. When Fey named the figure, Poehler laughed. "I think you should take the job," she said.

The cast members of "Saturday Night Live" are recruited from standup acts and from three comedy farm teams that tend to define the comedians they produce. The writer-performers from Second City (Dan Aykroyd, John Belushi, Bill Murray, Gilda Radner, Rachel Dratch, Amy Poehler, Horatio Sanz) are known for their aesthetic perfectionism. "They're tangled up in their own integrity," as Fey puts it. The performers who come from the Groundlings, an improv troupe in Los Angeles (Laraine Newman, Chris Farley, Will Ferrell, Julia Sweeney, Maya Rudolph, Chris Kattan), create vivid and eccentric characters. The writers who worked at the Harvard Lampoon (Dennis McNicholas, Michael Schur, Conan O'Brien) tend to emphasize the conceptual premise of a sketch. While each of the fifteen performers on "S.N.L." is expected to write (or risk getting no parts), some take to it more naturally than others. Fey characterizes certain kinds of Groundlings jokes, and especially Harvard Lampoon humor, as peculiarly male, founded in boyhood fantasies. "She's Chicago," Jimmy Fallon explains. "Dennis is Harvard. She'd do more jokes about having sex with a hobo, and he'd do more jokes about robots and sharks." Fey has contributed to a mostly friendly rivalry between the competing sensibilities, conceding that "the Lampoon people are very smart, obviously-they're helpful to have around."

Fey herself tinkers with a line's inflections and implications in a way that befits a Second City alumna. The details of human behavior-minor notes of pomposity, say, in apparently self-effacing speech-make her laugh, and she knows how to introduce those notes into sketches. She also knows how to update existing comic conceits subtly: when Billy Crystal reprised his Fernando character for the show's twenty-fifth-anniversary broadcast, in 1999, Fey surprised longtime staff members by learning the Fernando voice ("You look mahvellous") and writing jokes that suited it.

On "Update" she periodically slides into the kind of easy world-weariness that is associated with Jan Hooks, who is one of the former cast members that Fey most admires. At other times, she uses broad self-mockery and caricature, which recalls Gilda Radner's work, although when Fey claims in jokes that she can't get a date she's hard to believe. In fact, she may be alone among contemporary female comics in appearing, above all, distant and aloof-an object of desire.

Gender has been Fey's ace since she arrived at "S.N.L."-one recent sketch dramatized the barbarism of bikini waxing, and another cast Barbie as a fading beauty living with a gay man in Southern California-and she has spoofed stereotypes of women while taking on formerly neglected subjects, such as infertility, sexual abuse, and plastic surgery. When a male staff member asked Fey, who had just written a sketch that imagined a world in which old black ladies were Hollywood trophy wives, if her sketches were "anti-woman," she told him that the show's business was to make fun of people, and if it didn't make fun of women the female performers would have no parts to play. Now she has found a way of playing sexism for laughs, of telling audiences, "I can say this, but you can't."

Although Fey is credited with bringing moral authority to the set-the black-rimmed glasses she wears on "Update" add to this impression-she has also made the show more lewd. Raw humor has long been a part of Fey's repertoire. (She once wrote a piece for a workshop in Chicago that featured Catherine the Great complaining about life's inequity: "You can be a murderous tyrant and the world will remember you fondly. But fuck one horse and you're a horse-fucker for all eternity.") And since she became a head writer the words "whore" and "bitch" have flourished on the show. (After the invasion of Afghanistan, she announced on "Weekend Update," "For the first time in more than two years, women took off their veils and walked freely in the streets. Those whores.") Jokes have also become more graphic. "My mom had me when she was forty," Fey said in a personal aside one night on "Update." "This was back in the seventies, when the only 'fertility aid' was Harveys Bristol Cream. So waiting is just a risk that I'm gonna have to take. And I don't think I could do fertility drugs, because, to me, six half-pound translucent babies is not a miracle-it's gross." On another show, she told the audience, "Female inmates in the United States have been victims of sexual misconduct by corrections employees in every state except Minnesota. So, ladies, if you wanna rob a bank but you don't want your cooter poked, head to beautiful Minnesota, land of ten thousand lakes."

Male comics, particularly Bill Murray, Steve Martin, and Colin Quinn, have influenced her, especially with their comic rants-extended monologues shouted straight at the camera. On "Update," Fey frequently rants about political topics, as in:

President Bush was criticized this week for not having a clear stance on the Middle East crisis. You know what? Good. The only people with a very clear stance on the Middle East are the crazy people in the Middle East. I've had it with all of them. Yasir Arafat? Don't talk to us in English and say, "I agree to a ceasefire," and then turn around in Arabic and be like, "Hassan, let's do this." O.K.? We're onto you. We've got like two bilingual C.I.A. guys now. We know what you're saying.
And Sharon? When you're storming West Bank towns and bulldozing people's homes? Try not to look like ya love it. 'Cause ya kinda look like ya love it.

"What destroys comedy writers," Lorne Michaels told me, "is when they cling to something." Fey has won his favor because she will drop ideas that have run dry, such as her once-popular parody of "The View," ABC's morning talk show, which featured the catchphrase "I'm a loy-ya." She also risks new voices. Among these is her "Old French Whore!," a sketch involving haggard prostitutes who tell stories of revolting, drug-addled nights. The prostitutes are paired on a game show with clean-living Americans, who have to prop up their dissipated, despairing partners. Eventually, one of the Americans says, "I think my whore is dead."

Offstage, Fey is playful but proper. On the air, her delivery is like a lash-"Hey, kids, it's the great women of U.S. history! Collect all ten!" or "This is the hardest Bush has worked since that time he tried to walk home from Mardi Gras"-followed by a self-deprecating smile. Nearly all Fey's colleagues mentioned her ability to be mean and disarming at the same time. I heard her humor variously described as "hard-edged," "vicious," and "cruel." Shoemaker told me, "The fight you have in your head with someone, that you're never really going to have? . . . I think she plans one every day."

While I was sitting with Fey one afternoon in a café on Broadway, she admitted that she chronically prepares for the worst, in part by keeping zingers close at hand. But it's excessive, she realized: "No one's really coming at you." She had been reflecting on current events, and I expected to hear her customary tartness, but her voice faltered, and tears slipped down her cheeks. "In New York you get to have little moments of fear every day now," she said. "Right after September 11th, I thought, We got to get out of here. My dad talked to me about how important it was to go back to work. But it has not been easy. I remember I was writing jokes in my dressing room one Friday. I looked up and there was a guy on MSNBC saying, 'Anthrax has been found at 30 Rockefeller Center.' And I thought, I'm fucking in 30 Rockefeller Center. Thirty. Not even 45 Rockefeller Center. You do get the irrational feeling that they are specifically coming for you. And I got up, got my coat, walked out of the building, and I just kept walking. I was very upset. That night, I got a call from Lorne, and he said I was the only person who hadn't come back."

Others at "S.N.L." didn't know how to respond. "I do have to say that it changed the way we thought about her," Shoemaker said. "That was the first sign of fragility." Fey told me that she has been systematically imagining-and rehearsing-a knockdown fight with terrorists. She entered a course of psychodrama, a form of therapy that uses acting techniques to banish sadness, anger, and fear. In sessions, she said, she faces down imaginary terrorists, sometimes represented by chairs. She also punches a pillow that stands in for President Bush. Later, she surprised me again by mentioning that she had once been the victim of a violent street crime.

Her anxiety has shaped her work. On a show in 2001, Fey said, "On Monday, Attorney General John Ashcroft issued a terrorism warning, asking all Americans to be on high alert this week. . . . I think I speak for all Americans when I say, 'Bitch, I can't be any more alert than I already am. O.K.?' I'm opening my mail with salad tongs. I take my passport in the shower with me. I am watching so much CNN I am having sex dreams about Wolf Blitzer."

Another day, when Fey and I were walking around her neighborhood, on the Upper West Side, a man passing us spat on the sidewalk. When she turned to confront him, he looked up innocently. "Hey, dude!" she shouted. "Get a Kleenex!" The man slunk off in shame, as Fey, shaking her head in disgust, kept complaining. As in her college days, she looks down on misbehavior. "She's pretty monastic at times," Amy Poehler told me. "She's not the first girl to belly-flop into the pool at the pool party. She watches everybody else's flops and then writes a play about it." Fey goes out with the cast after the show, but she is self-conscious at parties and careful not to embarrass herself. She's meticulous about her diet, too. She lost thirty pounds in the year before she went on camera for "Weekend Update," and she now works out with a trainer and counts the point value of each meal according to the Weight Watchers system. (Earlier this year, People included her in its annual list of most beautiful people. "Don't mention it," she told me. "Ride it out.")

Fey's rigidity may be connected to her tendency to see the world in stark moral terms. ("She has very definite opinions as to what should be done about terrorists," Shoemaker said.) At work, Fey tempers her hard-line reputation by playing the nerd-by pretending that she's unfamiliar with, rather than disdainful of, the ways of the less temperate. Jeff Richmond told me, "I don't know if she's judgmental-maybe 'fascinated.' Nah, 'judgmental' is the right word." He went on, "She says, 'Why do people have to drink too much?' I've heard that in reference to-well, me." She and Richmond, who were married in a Greek Orthodox ceremony in 2001, bought a duplex at the top of a building off Amsterdam Avenue earlier this year. A fluke electrical fire and water from the fire hoses damaged it in the spring, but it has since been fixed up and painted chartreuse, although there's still not much furniture, besides a piano and an old school table. During her time off, Fey often sews or bakes cookies. "For some reason, I believed Nancy Reagan," she explained. "I believed that what she said, I should do."

Lorne Michaels waves off Fey's classification of herself as a square, and compares it to the tendency of the show's first cast to claim they were rebels. "This cast is young. They're ambitious. They pride themselves on being less self-destructive," he said. "But we didn't pride ourselves on being self-destructive in the seventies. People were experimenting with freedom. The spirit then was more fraternal than maternal." He added, "I think that being geeky is just another way of being Holden Caulfield or the Graduate. Comedy people are always outsiders."

On October 13, 1979, Steve Martin hosted the season première of "Saturday Night Live"-he played the Pope, an aspiring male model, and Carole King's boyfriend-and nearly half of all television viewers in America tuned in. The show can never expect to do so well again; last season, on average, its share was about thirteen per cent. Still, NBC is pleased: the show rivalled its ratings from seven years ago, when the average viewer had only forty-one channels to choose from. Today, the average is more than a hundred channels per household, and several of the cable stations, especially Comedy Central and HBO, have strong comedy lineups.

This fall, Fey is writing and performing as usual. Earlier this month, she appeared in a parody of "Queer Eye for the Straight Guy." Fey, dressed in pink, played a kittenish suburbanite whose life was made over by no-nonsense lesbians. On "Update," she seconded Rush Limbaugh's claim that Donovan McNabb, the Philadelphia Eagles quarterback, was praised too highly for his performance because he is black. She said, "Finally, someone has the guts to say what the liberal media doesn't want you to know: black people are not good at sports." She also flies to Toronto for a few days each week to work on the set of "Mean Girls." Having spent the summer on Fire Island rewriting the screenplay, she said she was happy to be "back in an environment of comedy snobbery," because "it's better for you."

Lorne Michaels told me, "There's a group of people who feel Tina can do no wrong in my eyes. But that's because she's just wrong less often than other people." Michaels went on in this vein for a few minutes, and then abruptly paused to ask a question that nearly everyone I had spoken to about Fey had asked: "What does she say about me?"