Black residents of the Washington area are still likely to face discrimination in their search for apartments to rent, despite widespread publicity and more than a dozen lawsuits that focused attention on the problem a year ago, a coalition of human rights and fair housing groups reported yesterday.

A six-month investigation, during which black and white people posing as prospective renters visited 111 rental properties in the metropolitan area, showed that blacks were discriminated against 57 percent of the time, with the highest incidence of bias found in Prince George's County and Northern Virginia. The Virginia study covered three jurisdictions: Falls Church, Alexandria and Fairfax County.

The federally financed study was a follow-up to a nine-month testing effort completed in mid-1986 that showed that blacks were discriminated against 53 percent of the time, with the most cases of discrimination found in Montgomery County and Northern Virginia. Organizers described the 1986 study of 266 rental complexes as the most extensive testing ever done of racial discrimination in the Washington area.

Black testers in the 1987 follow-up study reported encountering bias at 70 percent of the properties they visited in Prince George's, 62 percent of buildings in Northern Virginia, 57 percent of buildings in Montgomery County and 43 percent of properties in the District of Columbia. Blacks make up about 45 percent of Prince George's County residents, according to the Greater Washington Research Center. The 1980 census showed that nearly 9 percent of Montgomery residents are black, and the research center reported last year that about 65 percent of the District's residents are black.

In the latest rental bias study, rental property owners were determined to have discriminated if they told black applicants that apartments were not available but showed units to white applicants, or if they told black applicants apartments would be available at a later time than the dates given to whites, or if they discouraged blacks in other ways.

The rental agent at one Falls Church apartment complex showed black applicants rental units in bad condition or undergoing renovation on four visits, while a white applicant was shown an apartment in good condition, the study said.

"What happened most was that information was withheld from black testers," said Ellen Shogan, acting director of the Fair Housing Council, formed in 1983 by a group of metropolitan area clerics. Black applicants "were treated with a lot less respect and courtesy" and were asked more questions than whites about their credit history and the number of credit cards they held, she said.

Donald R. Slatton, executive vice president of the Apartment and Office Building Association, which represents property owners and management companies in the metropolitan area, said that he has not seen the results of the most recent testing but noted that he had doubts about the 1986 study because "a lot of {the findings} were attitudinal."

"Discrimination does take place, and it's wrong, and it's very bad business," Slatton said. He said he doubts that there is as much discrimination as the two studies indicate, basing his "opinion on what I know of the professional companies" belonging to his organization.

The 1986 investigation was conducted by the Regional Fair Housing Consortium, made up of human rights agencies of local governments, and the Fair Housing Council of Greater Washington, using a $200,000 grant from the U.S. Department of Housing and Urban Development. Teams of testers, with each team consisting of one white and one black tester, visited apartments in neighborhoods with black populations of 20 percent less than the overall population of the city or county in which they were located. Apartment properties to be visited in those neighborhoods were chosen at random from apartments advertised for rent in The Washington Post. The testers had similar incomes and backgrounds, and they shared most other characteristics except for race.

The follow-up study in 1987 covered a smaller number of properties, primarily because "we didn't have the funds" to cover as many apartment complexes, said Shogan. About 70 percent of the properties tested were selected under the guidelines used in 1986. The others had been involved in suits resulting from the first round of testing or had been subjects of complaints to the Fair Housing Council.