Foxchase Cinemas 3, a multi-screen movie theater in the suburban sprawl of Alexandria's West End, shines at nightfall like a city on the plain in the darkened expanse of high-rise apartments, condominiums, convenience stores and fast-food restaurants.

On a recent week night, hours after most of the stores and shops that also inhabit the Foxchase Shopping Center had closed, scores of cars--family sedans with baby seats, vans and pickup trucks--park as close as legally permitted to the theater's newly renovated facade of brick and Italianate columns.

In one section of the 650-seat theater, Kirk Douglas whoops it up in Australia's PG-rated hit, "The Man From Snowy River." In another, last summer's box office smash, "An Officer and a Gentleman," is back. But the real attraction of the Foxchase Cinemas 3 lies scarcely 20 feet away, where the soundtrack is likely to feature more moans and groans than high-toned entertainment.

This week's latest hit: "Irresistible," nominated for 13 erotic-film awards this year, according to the newspaper ad that lists the movie under Adult Entertainment.

Also showing, soon to be for its seventh consecutive year at Foxchase, is "Misty Beethoven," an X-rated movie classic starring Constance Money. Jimbo and Ron, two college-aged Alexandrians, say Cinemas 3's mixed offerings are a fine idea.

"It's clean and everything. And nobody has to know what movie you are going to see when you walk in that front door," says Jimbo, the only name he agreed to give. "This is just like any other theater, the way I see it."

Jimbo and Ron saw "Irresistible." They say it's the third time this summer they have paid their $3.75 to see an X-rated film at the theater. And, they add, it probably won't be the last time.

"Did you see those babes?" Jimbo says, referring to three young women who giggled their way to their seats in the darkened theater where "Irresistible" was starting its second run of the night.

Lots of nice people come to watch close-ups of naked people in the throes of cinematic sex, says the Cinemas 3 ticket-taker, a young woman with a teen-age face.

"You should see our regulars," she says. "They come two or three times a week."

To see the same movie?

"Yeah. They buy discount books of tickets," she answers with a half smile on her face.

One of the largest groups of patrons of the X-rated fare, according to the theater's ownership, is senior citizens. Silver heads staring at silver screens showing blue movies were apparent one recent night. But no raincoats. This was strictly a Bermuda shorts- and sports shirt-crowd.

"I do think it's a little unusual they have PG- and X-rated movies going in the same place," says a 31-year-old man who just took his 21-year-old fiance to see "Irresistible," a movie about a young man who is sexually bored with his wife and uses a time machine to satisfy his desires by making love to famous women throughout history.

"I think there's lots of variety here," says his fiance.

"We don't just come for the sexual end of it," he says. "We've come to see more than just the X-rated movies. This is a nice place."

Both asked that they not be identified.

With the exception of the hardcore films, Cinemas 3 does appear to be like any other suburban Washington movie theater.

The building is simple, architecturally compatible with the coin-operated laundry on its western side and Universal Beauty Supplies on its eastern side.

Inside, the theaters are cramped and plain compared with the elaborate, highly decorative theaters of Hollywood's boom years more than 30 years ago.

Next to the glassed-in ticket booth, a roll of quarter-hungry video games stand blinking and burping their electronic invitations to play.

And of course, like all movie theaters, there are tubs of hot, buttered popcorn and a candy counter whose brightly wrapped contents are stacked like bars of gold.

But the theater had to do something different, explains Cinemas 3 co-owner Alan Rubin, if it was to survive in a movie era that was spawning films with bigger and bigger budgets whose distributors were demanding bigger and bigger rental fees while competition with theater chains was growing more intense with every new release.

And so, seven years ago, "we brought the X-rated film in," Rubin says. "We did it out of necessity being the mother of invention. We're just little guys. It was just business."

Today, Rubin, who is also co-owner of the Biograph in Georgetown, says the hardcore films are an essential part of the theater's success.

"We have received absolutely no complaints," he says.

Alexandria Vice Mayor James P. Moran Jr. says as long as the theater management doesn't permit children to see the films and the showing of the films are not disruptive to the surrounding neighborhoods, "I'm not going to lose any sleep over it.

"There is an obvious desire for that type of diversion," says Moran.