"All right, take it from the top."

Stage lights come up on a grungy Formica table and chairs, a cashier's stand.

Characters: one very bored young male cashier, one high-strung, defeated bus girl.

Place: a two-bit cafeteria in New York.

Time: almost closing. She approaches the table next to him. He notices her compulsive cleaning and starts conversation. Nervously wringing her dishcloth, she suddenly explodes into meaningless chatter. No one, especially a handsome aspiring writer, has ever cared to talk to her. To stop trembling, she tries to clean the cashier's stand. Books, papers and assorted junk fall off.

This is a rehearsal of "Birdbath," a play by Leonard Melfi to be performed by the Georgetown Ensemble Theatre Company this weekend for the D.C. Recreation Department's one-act play tournament. The actors are not professionals.

Playing Velma the bus girl is Smithsonian Institution secretary Rosemary Regan. She got the acting bug two years ago, while working on her master's degree, when her professor gave students parts in a Shakespeare play instead of the usual term paper.

"He wanted us to ounderstand the dimensions of a play," she explained. "Once I stood up they couldn't make me sit down."

Regan is part of a sizable dubculture - made up largely of professionals, government workers and the like -- who devote as much as 40 hours a week to their lives on the boards in community theater.

"People know they can't make a living from it," says Karen Brooks Hopkins, producing director for the Jewish COmmunity Center's Chelm Players. "Professional theater is a difficult life. There's no money or security unless you're one of the few who make it . Family life is hard because you're not on a normal schedule with the rest of the world."

Chelm Players member Donna Birndorf spent years training as a dancer before deciding she didn't want that kind of life: The constant struggle to keep her body in shape and the fight tothe top weren't worth it. After time out for marriage and children, she was dying to go back - this time to acting. Now she wants to shoot for the big time, though she's not sure where her effort will take her.

For the Chelm Players, there's and additional attraction: They use old folk tales jokes and stories from the shtetl, the Jewish villages of Eastern Europe, in vigneties that help preserve cultural traditions.

Even without that added dimension, there's love of the theater, "a strong drive for professionalism," says Jane Squier, an actress with the Montgomery Players. "We're never paid but are still dedicated. And the rapport that grows within the cast is wonderful."

"I do this for enjoyment," says Marty Kushner of the National Credit Union Administration. "I won't even take a part in a play unless I like it."

"You have to be pretty good," says director Joseph Shubert, who works at the National Association of Educational Broadcasters, "but there's the freedom to fail."

Why the popularity of one-act plays?

For the theater group, it's a way to try out new directors and give actors and students a chance to participate, says Richard OChs, president of the Little Theater of Alexandria, since "The financial risk is much less."

Aspiring playwrights find the limited scope of the one-act play attractive. "It's easier for a beginning playwright to constructa one-act play," says Dick Long of the Woodley Players.