Dying is easy. Comedy's hard.

That adage is proved over and over again in "Comedian," an absorbing if frenetic documentary about Jerry Seinfeld's return to stand-up comedy after a two-year hiatus. Having retired his eponymous comedy series in 1998, Seinfeld clearly doesn't need the money he makes schlepping from Comedy Cellar to Comedy Stand. "Comedian" ostensibly follows Seinfeld over a year-long period of honing jokes and working out new material in tiny clubs, but it's really the chronicle of the restless, fearful, even pathological spirit that animates the most gifted comedians. What begins as an indulgent vanity piece (Seinfeld was a producer of the film) ends up as a fascinating portrait of creativity at its most compulsive.

Director Christian Charles caught up with Seinfeld early in 2000, when the comedian was beginning to go back to the small Manhattan comedy clubs where he cut his teeth in the 1970s. Blending in to a startling degree with the unknown artists who are vying with stage time, Seinfeld gamely adheres to the professional drill, waiting for his turn, trying out new jokes, enduring the occasional heckler. ("Is this your first gig?" one woman shouts out after he forgets a punch line.)

These short routines are a crucial part of the writing process for a comedian trying to put together a one-hour show he can take on the road: Bit by bit, as jokes succeed and fail, the comic builds what he hopes will be a full-length show. Until then, he must submit to this painstaking process of trial and error, which Seinfeld likens to "going to work in your underwear." Seinfeld's friend and colleague Colin Quinn calls it a boxing match where the comedian is going mano a mano with the audience, gloves off. Seinfeld agrees. "It's the smelly gym," he says, looking around at the smoke-filled room.

As "Comedian" traces Seinfeld's return to the stage, it also chronicles the career of Orny Adams, an aggressive young comic whom we meet when Seinfeld bumps him from the lineup at New York's Comedy Cellar. Charles spends a lot of time with Adams, following him to a comedy festival in Montreal and to his first appearance on the David Letterman show, and you can see that he wants to set the two men up as counterpoints: Each wants to be where the other is. But Adams is far too unappealing and, from the looks of his routines here, unremarkable a performer to deserve the screen time. "Comedian" is best when it focuses on Seinfeld's own quixotic search for his roots, beautifully embodied by the fact that he's traveling to and from his gigs in a Porsche and a private plane. "I was huge, I could be anywhere," he says at one point. "I'm in a comedy club in Cleveland."

"Comedian," which Charles unfortunately photographed in washed-out video and then edited with lots of frantic, jittery cuts, introduces a Seinfeld audiences didn't see on his TV show. In person he's edgier, darker -- sexier -- than his sitcom alter ego. And when the film really kicks in, right around the time he comes to Washington to try out his completed act at the Improv, what might have been a sentimental journey takes on the dimensions of something much more profound. (There's an extraordinary sequence, just before he goes onstage, where Seinfeld seems to have attained a perfect alpha state of zoned-out concentration.) More than an adventure or just work, comedy in Seinfeld's hands takes on the characteristics of an extreme sport: He doesn't do it because he can, he does it to prove that he can, to whatever cruel scorekeeper lives in his head.

Sprinkled throughout the film are encounters between Seinfeld and such friends as Chris Rock, Robert Klein, Garry Shandling and the king of the road warriors, Jay Leno. Many of the brief conversations reveal the fear and loathing that motivate so many men and women to want to make people laugh. The thing they fear and loathe the most, of course, is the audience. The thing they need the most is the audience, too. Those fans and hecklers and drunks and wannabes are never shown in "Comedian," but they are heard, like some unseen force of nature waiting to devour its prey. In fact, "Comedian" may be best appreciated as a monster movie, in which the protagonist overcomes all manner of trials to defeat the beast. By the time Seinfeld arrives at his destination, you can't help but feel happy and exhilarated and even moved by his triumph. Comedy's still hard, but our hero has lived to die another day.

Comedian (100 minutes, at Cineplex Odeon Dupont Circle) is rated R for language.

Jerry Seinfeld in "Comedian," a documentary by Christian Charles.