This time last year, Uma Thurman seemed to have everything a 32-year-old American woman could reasonably wish to possess: she was entering the third decade of a film career that began at age seventeen, when, as Venus, she literally emerged from a clamshell in Terry Gilliam's The Adventures of Baron Munchausen. That film was followed by a long string of quirky and demanding roles that established Thurman as the most idiosyncratic sex symbol working in films today. She had a husband and two children; in 1998, Thurman had married the actor Ethan Hawke, and that same year she gave birth to a daughter, Maya Ray. By last year, when they had a son named Levon, Thurman and Hawke—with their particular combination of karmic ambivalence and obvious ambition—had become the signature couple of Generation X.

"It was all pretty safe and warm," Thurman told me the first time we met this summer, in Vancouver, where she was filming Paycheck, director John Woo's science-fiction thriller. "But life is so wonderfully cyclical," she said softly and without irony. "Anyway, safe is never where I have wanted to be. In control, maybe, but safe? I don't see the point."

Thurman and her costar, Ben Affleck, had just finished work on Paycheck's climactic scene, which involved repeated explosions, a great deal of fire, and a harrowing escape. After Woo examined the rushes and dismissed the cast, we adjourned to a freezing, nearly empty trailer not far from the set. Thurman was still grimy and wearing a costume not much different from her daily attire: dark-green cargo pants, a plain white v-neck T-shirt, and work boots. Her hair was choppy, and her nails were trimmed (or bitten) to the quick. Thurman entered the trailer with two glasses of fruit juice and placed one in front of me; she then lowered herself into a white leather reclining chair and proceeded—unfolding one endless limb at a time—to lean her legs against the wall so that they rested far above her head. She remained in that position for more than an hour.

The past few months have not been easy for Thurman. Almost every day the gossip columns report on her troubled personal life, speculating widely that her marriage to Hawke—who had been seen often this summer in the company of another woman—is coming to an end. Thurman is frank and voluble; in Vancouver, though, her marriage was the one subject she didn't want to discuss. But when I asked how she and Hawke managed to juggle the many demands of travel, film schedules, and their responsibilities to two young children, she closed her lake-size blue eyes for a moment. Then she shook her head. "We haven't really been able to figure any of that out, to be honest," she said. "It's very, very tricky, and I don't know if there is a solution."

In Hollywood, it is never easy to keep from becoming typecast, particularly if you happen to be a nubile, six-foot blonde with cheekbones that could cut diamonds. Thurman's complex and highly acclaimed role in the 1990 film Henry & June included love scenes with Maria de Medeiros (who played Anaïs Nin) that provided the principal reason that film became the first to earn an NC-17 rating. Thurman spent many years running from her status as a sex symbol—turning a collection of hats, sunglasses, and baggy clothes into a kind of secular chador. But a disguise goes only so far for somebody like Uma Thurman because, as John Malkovich, her costar in Dangerous Liaisons noted when they worked together, she "has this Jayne Mansfield body and a horrifyingly great brain."

Still, Thurman never seems to opt for the easy route when a hard one will do. So two months after giving birth to her son, in the spring of 2002, she flew to Los Angeles and began to train eight hours every day for her role in Kill Bill, Quentin Tarantino's cartoonishly violent homage to the Hong Kong martial-arts genre. Thurman, who plays a vengeful former assassin out to get even with her boss, conceived the central character with Tarantino when they were making Pulp Fiction—a film for which she received an Academy Award nomination for her role as the drug-addled wife of the L.A. gangster Marcellus Wallace. Tarantino wanted Thurman to star in Kill Bill so badly that he put off the production for nearly a year while she was pregnant. "OK. What would Josef von Sternberg do in this situation?" Tarantino said when I asked him about it. "He is getting ready to do Morocco, and Dietrich gets pregnant. I mean, Uma is my Dietrich, for god's sake. I took the whole color scheme of the movie from her hair."

Thurman appears in nearly every scene of Kill Bill: Vol. 1 (the second part will be released next winter). She has made nearly 30 movies in the past fifteen years, and when I asked if this was among the hardest roles she had ever undertaken, she laughed. "No," she said. "Not among them. It was the hardest by far. Period."

Kill Bill opens with a stark shot of a blood-caked bridal veil, and it gets much more graphic from there. Thurman plays a character called the Bride, who is beaten brutally at her own wedding, then shot in the head by her former boss, Bill, played almost invisibly by David Carradine (he has a much more significant role in the second part). The bride and everyone else in the wedding party are left for dead. She doesn't die, though, but spends four years in a coma; and when she awakens, she sets off on a journey to find and then Kill Bill. To accomplish her goal, Thurman creates vast rivers of blood, and there are times during the film when she makes Hannibal Lecter seem like a deacon at a Baptist church.

Thurman never fires a gun in Kill Bill, yet she manages to murder about 90 people—most of them in a climactic battle in Tokyo with Lucy Liu, who plays O-Ren Ishi, the chief of the yakuza, who was also once one of Thurman's fellow assassins in a gang called the Deadly Vipers—a kind of evil version of Charlie's Angels. That fight scene was filmed in Beijing, and it took eight weeks to shoot, nearly as long as it took Tarantino to make Pulp Fiction. The violence Thurman commits is so extreme that it almost has to be viewed with a comic eye; any other approach would be too painful. Even before that fight, the Bride was forced to kill one of her former fellow Deadly Vipers in front of the woman's young child—a scene about which there was much debate. Tarantino doesn't make it easy on his characters; throughout the movie one is supposed to be solidly on Thurman's side—it is, after all, a revenge film—but you are also supposed to be afraid of her.

"There is no part of me that doesn't somehow get affected during the movie," Thurman told me. "I am covered in blood; I am thrown in the ground and buried alive. For some reason Quentin never tried to drown me or burn me, but other than that there is no sort of emotional or physical violation or assault that doesn't happen to my character. It's nowhere I have ever been before." I asked why she chose to make the movie. "I didn't," she replied. "I was never really offered the movie. I was just in it. One night when we were making Pulp Fiction we were bantering around, and I was talking about a character I wanted to play, and Quentin was talking about revenge movies. He wrote seven pages of the script right there. It was so neat because he wasn't Mr. Super Über-famous at that point. He was just this mad, exciting person."

To prepare for her role, Thurman lost 50 pounds and turned her body into something harder, more powerful—and a bit more frightening—than she suspected was possible. Carradine was amazed by what she put herself through. "Nobody trained harder than Uma," he said. "She had a ten-week-old baby, for Christ's sake. But she turned herself from an overweight new mama into something tougher than a marine. She is the Clint Eastwood of women in this movie. But there is a soft loveliness to her that is incredible." Thurman worked with the Chinese martial-arts expert Master Wo-Ping Yuen (who choreographed all the fight scenes in The Matrix) and Sonny Chiba, the legendary star of samurai and martial-arts films. Thurman was eager to describe her training regimen, still not quite believing that she had lived through it.

"I would go in the morning, and you had to be on time," she said. "It was very important to show respect for the team. I would get on a treadmill and run or walk and then stretch. Then there were the kicks." Thurman was required to practice dozens of kicks each day. I must have seemed unimpressed. "You kick for an hour," she said, her voice rising just a bit. "Try it. Forget the fancy machines. Lift your legs enough times and you will die." Thurman also spent hours every afternoon learning how to wield a samurai sword; at first just how to hold it, then to swing it, and finally to use it to cut properly. She became proficient at falling and rolling with a razor-sharp length of metal in her arms and competent enough to hold the sword while being thrown around in a fight.

Finally, to bring her weight down more rapidly, she worked with conventional trainers after the samurai instruction was completed every day. Thurman often thought about quitting. "I was nursing the whole time. . . . I was saved by my baby, who was in the dressing room. Whenever he got hungry I could take a break. That was my one condition. And nobody could say a word."

Since Thurman has two young children, I wondered if, after half a lifetime in the movies, she had considered taking the mommy track. "I did," she replied. "I took almost two years off after Maya was born. When I first became a mother, I would break into hives if I went out to exercise. It was that feeling that I had to be with the baby, and I didn't feel free or comfortable unless I was. But I realized after having the second child that I need to work. I give all my extra time to the kids, of course, but for the first time in years I don't feel emotionally conflicted about work, and I love that. I never knew that I could do this kind of role; I was always a talker and a sitter. A catlike person. So to have done something for once in your life that has exceeded your understanding of what you thought you could do—that's a pretty terrific feeling."

Thurman's unconventional film career—she veers between playing endearing oddities like Glory in Mad Dog and Glory and big-budget movie roles like Poison Ivy in Batman & Robin—is an extension of a most unusual childhood. Thurman was raised largely in New England, with the occasional year spent in India, while her father, who is now professor of Indo-Tibetan Buddhist Studies at Columbia University, taught at Amherst College. Her mother, Nena, is a psychotherapist (and a former Swedish model) who was once married to the LSD guru Timothy Leary. ("It irritates her immensely that that is in every piece about me," Thurman, who also had a brief first marriage to the actor Gary Oldham, said. "But I know it's a fun hippie fact.")

Uma and her three brothers—Ganden, Dechen, and Mipam—all were named after Buddhist deities. "Sometimes it amazes me how passionately overeager I was to start my life," she said. I asked why that was the case. She threw her arms up and shrugged her shoulders. "It's a question for the shrinks. But I was. I wanted to play with the grown-ups." Thurman's father, Robert—known to generations of students as "Buddha Bob" because he was the first American to be ordained as a Tibetan monk—agreed. "Uma knew what she wanted to do 100 percent," he told me. "We call it karma, attitude from a former life. When she was very small, we once went into a store and she was picking out dresses like a professional shopper. I was a very junior professor, and I thought she had expensive tastes. And I said that out loud, and at the age of four she turned around and said, 'don't worry, daddy, I'm going to be a big, famous movie star, and I will buy my own clothes.' "

By the age of fifteen, Thurman was already in Manhattan going to auditions. Her unique look—not exactly European but clearly not an American Barbie, either—and her cool, intelligent demeanor permitted her to carry off roles most American teenagers wouldn't even have tried. "She is so oddly beautiful," Stephen Frears told me. Frears directed her in the role of Cécile de Volanges, the virginal convent girl who was seduced on a bet by John Malkovich in Dangerous Liaisons. "Frankly, she intimidated the hell out of me." I asked how a teenager working with veterans like him, Malkovich, and Glenn Close could do that. "Well, she was so beautiful that I got flustered sometimes, but she is so smart that you better never make the mistake of treating her like just another incredibly pretty face."

Thurman has always been ambivalent about her beauty, and about glamour in general. She was gangly as a youth—all elbows and knees—and much taller than the other girls, not to mention the boys. She will never say it directly, but Thurman clearly considers making a living by being beautiful a bit unseemly. In fact, Tarantino told me that they have often squabbled about her hair color. "She always wants to be a brunette or have black or red hair or no hair or something," Tarantino said. "And I am always whining like a ten-year-old, saying, 'You are blonde, you are blonde, you are blonde.'" Thurman says she simply wants to put beauty in perspective. "It's all tremendous fun, nothing more and nothing less. I have always loved fashion and the whole dance of being a woman: the art and artifice of it and the playfulness of femininity."

Thurman has been the face of Lancôme for several years, and I wondered why a woman who has struggled so hard to avoid being seen solely as a sex symbol would allow herself to earn millions of dollars as, well, a sex symbol. "It was a sign that I had stopped being insecure about who I was and what my looks mean," she said. "The fact that I was not afraid anymore of what people would say about me; my God . . . ten years ago it would not have been possible. I had worked so hard trying to find my street cred and fighting being dismissed as a tall, blonde female person."

Still, she makes a point of mentioning that her contract with Lancôme has ended. She seems similarly conflicted about the fashion world, even though she has become one of its more visible icons. "One of the things that struck me at fashion shows is how great these incredibly thin women look in photographs but how in real life it's too thin. . . . They would be more attractive if they were a little heavier. And I actually don't think this desire to be rail thin is as pandemic aesthetically as the fashion world presents it to be. I don't think men prefer women to look like that; in fact, I think it's a unique kind of fetish. I understand the impulse, though. For women there is a great fear of losing control of your body and becoming overweight. If you are pregnant, no matter who you are, you do lose control and it's quite a shock. And then to have to deal with the aftermath. You ask yourself, what am I going to do with this body? Is it going to come back? Will I change? It's very frightening."

A few weeks ago, I met Thurman for breakfast at a tea shop she favors near her apartment in New York City. It was a grim September day, and I watched as she edged her way up Broadway. She was dressed casually, and from far away she looked like any other incredibly tall beautiful blonde woman you might encounter on a New York City street. It had started to rain heavily, but Thurman, whose head was covered by a mustard-colored fedora, didn't seem to mind.

She looked different than she had in Vancouver; some of the muscular marine look had given way. She was tanned, relaxed and a few pounds heavier; her face, which for Kill Bill seemed like it had been chiseled from granite, looked softer and the better for it. Thurman ordered Russian caravan tea with a scone, "and bring cream and jam and everything else," she told the waitress. She was wearing a tan, v-neck sweater set with plain Levi's and chocolate-brown suede shoes. She kept her hat on throughout breakfast.

Thurman had seen Kill Bill for the first time the day before, and she seemed relieved. She wouldn't guess whether the film would succeed, but her father had told me that one reason she made Paycheck was to have another movie in theaters this year—just in case. By Labor Day the gossip about her marriage had risen to a supermarket-tabloid level, and she was no longer able to dismiss it. Her brothers were even quoted in the New York Daily News and other papers suggesting Hawke had better watch himself. "I want to kill him," Mipam, who is a model, said after appearing in a Helen Yarmak show. He then said a few unprintable things before concluding, "I can't believe what he's done to my sister."

Thurman's friends are protective and, taking their cue from Uma herself, have been unwilling to talk about the situation. Thurman has been in the public eye for so many years that she says she learned long ago to ignore gossip—or at least to treat it with amused disdain; still, I did ask if lately she minded it more. "Not usually," she replied. "But sometimes. You know, I think it was Katharine Hepburn who had the best answer to that. She said the only time it hurts is when it's true.

"I am with the kids," she said, "and I am committed to taking the fall off. Then we will see what happens." She told me that she and Hawke had not had a serious conversation about the future, and she was unsure whether their marriage could continue. I asked if, in retrospect, working on Kill Bill for 156 days just weeks after she'd given birth could be viewed as a mistake. "I can never answer those questions," she said. "I am happy I did what I did in my life. I would do everything again. In my whole life. Of course you wish you could delete the mistakes and the stupid things you said. But it doesn't work that way. You can't go back and pull out the few unpleasant moments and still be who you are. You have to live it out." When I asked her father if he was worried about her, he said absolutely not. "If Uma decided to quit films tomorrow and come home and be there with grandpa and grandma and her wonderful children, it would be fine with us. It would be a problem with her public, who would be deprived of her luminous quality, but I wouldn't mind a bit. I don't worry. She will do whatever she needs to do in her life."

What that will be, at the moment at least, is unclear. "I am comfortable with myself," she told me quietly. "It took a while, and it was not always easy. I know that I will be unpacking what it took to do this film for a long time. It was done at a great cost, a tremendous cost, on every level. I am not the same person now that I was before the movie. I don't have the same life."