They are called "adult bookstores," but the books for sale there - paperbacks with titles like "Viet Cong Defilers" and "She Wanted Her Daughter" - are far and away the least popular and least profitable part of the business.

The heavy traffic is in movies, for viewing both on and off the premises; magazines, packed with photographs of people engaged in sex or trying to look seductive; "rubber goods," and medicinal and cosmetic "sex aids."

The magazines are arranged by category. "Girlie Magazines," "Boy-Girl," "Bondage" and "Swingers" are signs commonly found above the display racks.

Excessive browsing is frowned on. The magazines themselves are generally wrapped in plastic, and in one downtown store an almost plaintive sign admonishes customers: "Tell us what right have you to open and read magazines if you have no intention to buy?"

Although some stores also sell books and movies that involve children, animals, or sex liberally mixed with violence, these are rarely if ever on open display. Former pornography magnate H. Lynn Womack claims that the size of the traffic in such materials has been grossly exaggerated:

"People are impressed by the farout things. For example, God knows how much nonsense we've heard about the exploitation of children in pornography . . . The number of pederasts in America is, statistically speaking, so small - there are no norms, psychiatrically, for pederasts. Who in their right mind, just as a business proposition, would print books aimed at pederasts?"

The books, magazines, rubber goods and sex aids are usually arrayed in a brightly lit front room, in plain view of the cash register. But the level of illumination drops severely as a patron walks into the peepshow area, where a quarter will purchase a two-to three-minute look at a scratchy 8mm film projected, TV size, on a plywood wall.

In some stores the corridors that lead to the peepshow booths are heavily populated with loiterers, and the booths themselves, regardless of the character of the films shown there, are used as homosexual meeting places.

Other stores prohibit loitering. "More and more (of us) don't want two people going in at the same time," said one owner. "You don't want a heterosexual fellow feeling afraid."

Although the atmosphere of a store depends on its location and ownership, a few generalizations can be made about clientele. The customers are overwhelmingly male, white, cleancut and well dressed - "your coat and tie group," says H. Lynn Womack, ". . . the guy who is living in Bethesda with a wife who went to Vassar or Wellesley and he's so tired . . . he needs to refurbish his fantasy life."

While owners insist their stores are a boom to any neighborhood, they often employ trickery in quest of a lease. "Dennis (Pryba) and I bamboozled the landlord at Andrews Manor Shopping Center," says Womack. "Went out and had serious discussions with him about a bookstore, and he was telling me all about how we should put in study guides and so forth. And I listened very carefully and very respectfully because I wanted to lead him down the primrose path so he would not put in that little proviso that you cannot sell adult books."

On the other hand, landlords who knew perfectly well to whom they were renting sometimes find it advantageous to claim after the fact that they have been hoodwinked. Many landlords, far from refusing to deal with adult bookstores, merely jack up the rent.

Just how profitable is the adult bookstore business? Womack says there is a popular misconception "that somehow if you're printing a legitimate magazine the paper costs money, but if you're printing smut you're getting the paper free."

And "the amount of theft is very high," he adds. "The police don't care. Our experience was, we were never able to get a conviction on theft in our stores. The judges just weren't interested . . .

"When bookstores first came on the scene you had this vast, untapped market of millions of people who'd never seen this material. You don't have that market now . . .People laugh . . . they read these (newspaper) accounts and the people who own the stores have apoplexy."