Vienna officials have warned the owners of the town's two movie rental firms that they cannot rent R-rated movies in which "a buttock" or even a portion of a breast is visible, unless they get a special-use permit from the town.

The town goes into minute anatomical detail in its six-year-old zoning code to delineate the disapproved portions of the body.

One of the firms said to be in violation of the code, Shaffer TV at 123 Maple Ave., applied for the special-use permit yesterday after zoning administrator Robert Curry told owner Jay Baer he couldn't "rent any films showing flesh," Baer said.

Curry said a second store, the two-month-old House of Video at 130 Church St., is ineligible for a permit and must stop leasing films that show exposed buttocks and breasts. That means eliminating close to half of the shop's 460 movies, including numerous Academy Award winners, says owner James Zahand.

Both movie-rental firms are within a few hundred yards of the Vienna Theater, which often shows R-rated films. The theater is currently showing the James Bond movie "Never Say Never Again," which is rated PG.

The theater is "covered by a grandfather clause," a town zoning official said yesterday, because its owners were showing sexually explicit movies before the zoning code section governing films was adopted in 1977.

Town drugstores carry magazines in which undraped buttocks and breasts occasionally appear, but the magazines, like Playboy and Penthouse, are sold in brown wrappers under a Fairfax County ordinance.

One drugstore manager said yesterday he kept such magazines under the counter because "a town ordinance requires it."

According to Town Manager Brackenridge H. Bentley, there is no such ordinance, but a lot of people must think there is. "I recently got a phone call from a woman in the Chicago area who wanted a copy of the ordinance so they could duplicate it," he said.

Bentley acknowledged the zoning regulation may be giving the town a prudish reputation, but said it was needed "to keep out dirty book stores and movies." The present crackdown on rental movies stems from "a number of citizen complaints" Bentley said town officials had been getting.

Fairfax Commonwealth's Attorney Robert F. Horan Jr. yesterday questioned whether Vienna's code could survive a court challenge. While state law permits localities to adopt regulations controlling obscene materials, Horan said, the bottom line "is what is obscene" and "a breast or a buttock" are not likely to meet that test.

If Vienna's code is constitutional, added Horan, "Even the Mona Lisa's in trouble."

House of Video owner Zahand said yesterday he plans to continue renting R-rated movies as long as similar fare is available at the Vienna Theater, in drugstores and Fairfax County libraries.

County supervisors this summer pressured the Fairfax libraries, which lend R-rated films, to require borrowers to prove they are at least 18 years old. The driving force behind the board's action was Centreville Supervisor Martha Pennino, a Vienna resident.