Rap Inc.'s 15-year lease on a building in Adams-Morgan expires today and the head of the drug rehabilitation program said he had not been able to find new quarters.

Ron Clark, RAP's executive director, said the program's headquarters at 1731 Willard St. NW houses 53 residents who are undergoing rehabilitation.

"I don't know what will happen" to the program, which receives funds from the city government, when the lease expires, he said last night.

"We haven't been able . . . to find another building," he said, expressing the belief that the difficulty may stem from the resistance of community residents to having drug treatment programs in their neighborhoods.

While endorsing the goals of programs such as his, he said, residents typically say, "Why don't you do it someplace else?"

His landlord, the William T. Brawner real estate firm, which has made available the Willard Street property for $1 a year, has offered him new quarters, but the program would need a zoning change to occupy the site.

A Brawner official said he had understood that RAP had "apparently been negotiating for temporary housing with the District," until it could win zoning approval for the new site. But the official, Tim Tenhet, said he learned this week that those negotiations "might be falling through."

He said it was still possible that something could be worked out soon.

"It's been a long relationship," and "they've been good people," said Tenhet, the commercial property manager for Brawner. While Brawner is "not going . . . to force them out," he said, "I've told them we are going to have to take the building."

Clark said 800 drug users have successfully graduated from RAP, one of Washington's oldest drug rehabilitation programs.