SummaryWe examine changes and stability in risk behaviors and HIV-1 seroprevalence among heterosexual injection drug users (IDUs) over 13 cross-sectional surveys, 1986–1992. Interviews (n = 5,956) were conducted with IDUs in street settings and drug detoxification clinics over 6.5 years, and respondents were tested for HIV-1 antibody. Trends in use of condoms and bleach and HIV seroprevalence were assessed using multiple logistic and linear regression analyses. The percentage of time condoms were reportedly used during intercourse among men increased from 4.5% to 31.0%. Among the declining population of IDUs who reported needle sharing, reported use of bleach increased from 3% to 89%. Significant changes in use of bleach 100% of the time were reported: 29.8% in 1988, 52.8% in 1990, and 40.0% in 1992. HIV seroprevalence doubled from 7% in 1986 to 14% in 1987. Post-1987 fluctuations in HIV seroprevalence were not significant. Significant changes in risk behaviors among IDUs were reported over the study period. These changes coincided with the implementation of HIV prevention in San Francisco, including outreach programs, HIV testing and counseling, bleach distribution, and syringe exchange. The moderate and stable rate of HIV seroprevalence beginning in 1987 parallels self-reported reductions in risk behavior.