Sera from 500 (496 male and 4 female) consecutive patients with sexually transmitted diseases (STD) were examined for the presence of HIV1 antibodies. The serological tests were done using the ELISA (Wellcozyme) and confirmed by the western blot (Biorad). Sixty (12%) of the 500 patients were HIV-1 antibody positive. Seropositivity varied with the type of STD. A positivity rate of 16% seen with genital ulcer disease is significantly higher than the 7% prevalence rate seen in STD patients with urethral discharge. Infection with more than one kind of STD increases seropositivity significantly. Of the potential risk factors identified during the interview it seems that only shaving at barbers' shop is positively associated with seroprevalence. This study suggests that the presence of STDs is associated with an increased HIV-1 seroprevalence. Therefore, any effort to reduce HIV-1 infection should aim at the control of STDs.