Halfway through the prologue to Miguel Pinero's play, "The Sun Always Shines for the Cool," you begin to wonder: Why buy a ticket to this very realistic glimpse of the world of pimps and prostitutes when you can go to Thomas Circle, a mile or two down 14th Street, and see essentially the same show of nothing.

One answer is that Pinero's play (having its world premiere performance at the Back Alley Playhouse, 1365 Kennedy St. NW) shows that specialized world from the inside, as he did with the world of prison inmates in an earlier Back Alley production, "Short Eyes." Both plays have minor technical problems, but in a good production (and this one is very good) they generate a convincing atmosphere and dramatic power that make the problems seem unimportant. If you like hard-core realism, you will like Pinero.

But search under the heavy and precise details of scenery, costume and dialogue and you find pure melodrama: the story of Viejo, an aging pimp just out of jail and how he saves his daughter from being "turned out" (made a prostitute) by a younger pimp, Cat Eyes. The final confrontation scene, in a crowded bar, reaches a smashing climax.

The cast is generally excellent, and some performances are brilliant - notably Elliott Hill in a small but perfectly realized role, but also Diego Zuniga, Ray Green, Freddy Alves, Richard Ferrone and Stanley Earle Sellers Jr.

"The Sun Always Shines for the Cool" will be at the Back Alley, Thursday through Sundays, until July 10.