In order to measure changes in HIV-related behaviors among heterosexual alcoholics following treatment, we conducted a prospective cohort study of 700 self-identified alcoholics recruited from five public alcohol treatment centers, all of which included HIV risk-reduction counseling. Respondents underwent an HIV antibody test and interviewer-administered questionnaire at entry to alcohol treatment and after a mean of 13 months later. Compared to baseline, at follow-up there was an overall 26% reduction in having sex with an injection-drug-using partner (23% versus 32%, P < .001) and a 58% reduction in the use of injection drugs (15% versus 37%, P < .001), along with smaller improvements in other behaviors. Respondents also showed a 77% improvement in consistent condom use with multiple sexual partners (35% versus 20%, P < .01) and a 23% improvement in partner screening (71% versus 57%, P < .001). Respondents who remained abstinent showed substantially greater improvement than those who continued to drink.