IT'S SATURDAY, 2:30 a.m. The last strains of "Born in the USA" fade into the night as "last call" booms across the bar. No way you're ready to call it an evening. But what's left besides the local Little Tavern?

Bowling! Exactly! And don't be surprised to find that a lot of other folks have the same idea.

Rinaldi's Riverdale Bowl, the only "never-close" alley in the area, has been offering 24-hour bowling since 1975. And on weekend nights, patrons can sometimes line the hallway for hours at a time waiting for an open lane.

"It's just a lot of fun," says Gwendolyn Jenkins, a 29-year-old postal worker who waited two hours with her husband, David. "About two years ago, some friends at work asked me to go bowling," she says. "I thought they were crazy . .. But since that night, I haven't misse one weekend in two years. I love it."

Myron Klopman, a 27-year-old film editor in New York says he started bowling while studying at the University of Maryland. "When everything closed in the evening, we'd come here and bowl all night," he says. "Whenever I'm in town, I still come back."

Maybe you'd like to give late-night bowling a chance, but 2 a.m. is a bit past your bedtime. Places like Congressional Bowl in Rockville may be right up your alley. Every Saturday night at 11 sharp, Congressional turns off the house lights and bathes only the lanes in individual deck lights, and a disc jockey begins spinning records, "very old to very new," for Rock'n'Bowl.

"This is fantastic," says 32-year-old Charna Goldin from Rockville as she rolls a spare to the accompaniment of Pat Benatar's "Hit Me With Your Best Shot."

"This is a nice alternative," she says. "I like the music and the low lights. It's a good way to meet people."

Wayne Sikes, 19, from Wheaton, also likes the idea but he isn't having as productive an evening as Goldin. Sikes' second roll winds up a gutter ball. "I'm in tatters, I'm shattered," mouths Stark along with the Rolling Stones."

"We began this idea only a few months ago," says Congressional manager Wendy Pashkoff. "We wanted to introduce bowling in a new light to the audience and it has been very successful."

Not every alley has been happy with rock and bowl. Brunswick River Bowl in Bethesda recently abandoned its two-year experiment with "moonlight bowling" because it interfered with its regular bowlers: "The music was too loud, and there were too many people trying to sneak in alcohol," says a spokesman for the alley.

Congressional's Pashkoff, however, says, "We've never had any problem with drunk or disorderly conduct. The people who come here come for a good time, not to cause trouble."

And a number of other area alleys are pleased with their Rock'n'Bowl nights, among them the Fair Lanes in College Park, Laurel and Shady Grove, and the Reston Bowling Center in Reston.

"The response has just been super," says Shady Grove day manager Marilyn Whitmore. "People love bowling to the music with only the low lights on. And we find that people who come in for the first time during this period usually come back during regular hours. It's a great way for people to discover bowling."

Besides its 24-hour operation, Rinaldi's Riverdale has another gimmick to help its customers discover bowling -- computers. Along with Bowl America-Dranesville (in Herndon), this alley offers computerized scoring that keeps track of all rolls and automatically prints your frame score after each turn.

"A lot of people were turned off to bowling because they didn't know how to keep score," says Rinaldi day manager Irene Divver. "But now with our new computers, everything is done for them. So now they can relax and just enjoy the bowling."

Prissy Robinson, 19, of Glenarden, agrees. "I love these computer You know that if the lane is empty next to you, they'll let you turn on MTV on the screen. It's great."

"Go Go's are not the thing anymore," adds Robinson. "Here you can come, bop around and not worry. It's just a real fun and healthy atmosphere."

Good exercise, fun for all ages, challenging. Is there any complaint concerning the sport? "Yes," says Divver. "Why isn't bowling in the Olympics?"

But before you can answer, she says, "I guess the best thing about bowling is every frame, every roll is a new challenge. You always have the chance of that next strike, that big game." ON A ROLL

Here's a sampling of options for late-night or computer bowling: BOWL AMERICA-DRANESVILLE -- 1108 Dranesville Road, Herndon. 703/430- 1350. Computer scoring. CONGRESSIONAL PLAZA BOWL -- 1665 Rockville Pike, Rockville. 301/881- 6633. Rock'n'Bowl, Saturday night 11-2, $6 (shoe rental included). FAIR LANES COLLEGE PARK -- 9821 Baltimore Ave., College Park. Rock'n'Bowl, Saturday 10-1, $5, shoe rental 94 cents. FAIR LANES LAUREL -- 15013 Baltimore Ave., Laurel. 301/490-6006. Rock'n'Bowl, Friday and Saturday nights, 1-3, $6 (shoes included). FAIR LANES SHADY GROVE -- 15720 Shady Grove Road, Gaithersburg. 301/948-1390. Rock'n'Bowl, Friday 12-2:30, $6, shoe rental 94 cents. RINALDI'S RIVERDALE BOWL -- 6322 Kenilworth Ave., Riverdale. 864-6633. Open 24 hours a day, seven days a week; also computer scoring. RESTON BOWLING CENTER -- 1805 Michael Faraday Court, Reston. 703/471-9666. Rock'n'Bowl, Saturday 11-2, $6 (includes shoes); Monday 9:30- midnight, $4 (includes shoes.