D.C. Mayor Marion Barry warned more than 80 representatives of the city's 37 Advisory Neighborhood Commissions yesterday that it will cost the city dearly to distribute group homes for the mentally ill and others equally throughout the city.

"A four- to five-bedroom house in Ward 3 probably costs three times as much as the same size house in Ward 7 or 8. If you want us {city government} to spend that money then we will," Barry said.

"But when I do that I don't want to hear from you that you think it's outrageous that I'm spending the money for one house that could pay for two or three in Ward 4," he said at the city's semiannual ANC conference.

His question to the audience, "Do you want us to spend that kind of money for one house?" was met with loud applause.

Last month the District paid $2.9 million for a mansion in Georgetown to house 24 emotionally disturbed youths. The purchase, which signaled the city's intent to acquire more group home properties in affluent areas, was immediately met with a lawsuit from angry Georgetown residents. The purchase follows criticism from some about the city's unbalanced distribution of group homes, which range from 158 in mostly middle-class Ward 4 in north-central Washington to just 23 in the largely affluent Ward 3 in Northwest.

Barry told the ANC members yesterday that he will send out a citywide mailing explaining the need for group homes and the types of people housed in the homes. The District government must expand the number of group homes from 586 to about 900 in the next four years because of the deinstitutionalization of several city facilities, including St. Elizabeths Hospital.

Unlike the previous ANC conference on June 27, in which a broad range of city affairs was discussed, the meeting yesterday focused primarily on health and custodial care issues.

The principal speakers were Dr. Robert Washington, D.C. mental health commissioner, who discussed deinstitutionalizing and group homes, and Dr. Reed V. Tuckson, city public health commissioner, who talked about AIDS and its impact on the city, including the need to open homes for AIDS patients.

"I'm most concerned about the drug abusers who are sharing needles and spreading AIDS," Tuckson told the group. "Every time you don't let us open a drug treatment facility in your neighborhood you're writing a death sentence for this city."

Tuckson said the city's 323 ANC commissioners will "go down in the history books" for how they handle the AIDS crisis. He added that the city government "is going to open some houses for AIDS victims whether you like it or not."

Helen Mitchell, a commissioner from ANC 4C, which represents the Petworth area, suggested to the mayor that ANCs should canvass their communities for houses that might be acceptable as group homes and make recommendations to the city where it could open the facilities.

Vernon Palmer, a staff assistant for ANC 2B in Dupont Circle, told Barry that the city should ask the organizations that operate group homes to have ANC liaisons.

"I agree with that and we'll look into that," Barry responded.

On Tuesday, D.C. Council member H.R. Crawford (D-Ward 7) introduced a bill that would require the equitable distribution of group homes throughout the city. It would direct the mayor to come up with a formula for such a distribution.