It’s a little jarring when you realize Kenneth Lonergan is 36. Anybody who has seen This Is Our Youth , his piercing, sardonic look at the misspent days and nights of three Upper West Side post-adolescents, would swear he just dashed it off between classes (or instead of going to classes) at Hampshire or Princeton.

Lonergan says the play reflects his life circa 1982 pretty accurately -- "I borrowed stuff from absolutely everyone I was friends with and put it all in the play" -- but he’s sometimes surprised that those experiences still ring true. "I don’t really have a sense of what it’s like to be 22 in 1998," he says. "But younger people seem to respond to it, so I guess it’s still relevant."

He’s actually more worried about the older crowds right now. This Is Our Youth was first performed two years ago by the ultrahip New Group, and directed by Mark Brokaw. It was expected to vault into a lucrative commercial run, but nothing happened for "a combination of reasons, mostly theatre availability and cast availability." The current production, again directed by Brokaw and starring two-thirds of the original cast, is playing at Second Stage for a subscription-heavy (read: older) crowd. “I think a lot of older audiences watch it and shudder a little,” Lonergan says. “Still, you hope you can be very specific, but you also hope it will carry over to people with other, very different backgrounds.”

The play looks at three kids with too much brains, too much money, too many drugs and precious little of anything else. Warren (Mark Ruffalo) idolizes Dennis (Mark Rosenthal, the only new cast member), mostly because Dennis deals a lot of drugs, gets his share of women and never felt the need for college. (Warren managed a year or two before leaving.) But Warren still has a romantic streak and an occasional urge to do the decent thing, even if all the pot makes it hard for him to remember what that is sometimes. After he stumbles onto both Jessica (Missy Yager), an earnest Fashion Institute of Technology student with problems of her own, and $15,000 of his dad’s money, all in the same day, the three characters lurch their way into deeper knowledge about themselves and the bizarre choices that can turn kids into adults much too quickly.

Lonergan’s early days mirror those of his characters. After attending a progressive Central Park West high school -- the kind where, as one Youth character puts it, "they think it’s gonna cripple you for life if they teach you how to spell" -- he only lasted one year at Wesleyan. He eventually enrolled in the drama writing program at New York University, but not before having his share of wild times with his share of aimless friends on the Upper West Side. Part of the rehearsals of Youth involved walking the cast around his old stomping grounds. Lonergan has almost finished another play that he’s "eager to do," but his immediate future appears to be in Hollywood. He says the screenplay for the upcoming "Analyze This" is barely recognizable as his anymore -- "but, hey, it paid for the last three years." He’s currently working on a modern-day Rocky and Bullwinkle script for director Des McAnuff (Broadway’s Tommy ) and is about to direct his first movie, "You Can Count on Me."

"It’s pretty different writing for movies," he says. "It’s somewhat paradoxical: As a playwright, you have so much say over what happens, but at the same time, the limitations are so much greater. If you could set up a camera during the two-and-one-half weeks of rehearsal and film every take, you could put together easily the greatest performance ever."

Lonergan is clearly thinking ahead to the movie of This Is Our Youth . He is scheduled to direct the film as well as write the screenplay "unless it turns out I’m a terrible director after this other one. I think it should work because (1) I have a very clear idea of what I want; and (2) I have no idea what I’m doing and know it, so I have no qualms about asking anyone and everyone around me for help."

--Eric Grode