ObjectivesTo determine trends in HIV infection and risk behaviors among street-recruited self-identified gay and bisexual male injection drug users (IDUs) in San Francisco.MethodsTrends in HIV infection and risk behaviors were calculated for gay/bisexual (n= 1594 interviews) IDUs in 26 semiannual cross sections from 1988 to 2000.ResultsHIV seroprevalence among gay/bisexual IDUs decreased from the range of 35% to 45% in 1988/1989 to 25% in 1996 and then began to increase, reaching 42% in 2000. In contrast, HIV prevalence among heterosexual male IDUs remained stable during the study period. For gay/bisexual IDUs, injection and sex-related HIV risk behaviors declined modestly throughout the study period. As of the last cross section (July 2000), however, over a third of respondents reported recent syringe sharing or unprotected anal sex.ConclusionsGay/bisexual men who inject drugs continue to be at elevated risk for HIV, suggesting that interventions such as amphetamine drug treatment and sexual risk reduction programs targeted at this population are needed.