The prevalence of HIV-infection was studied in a district hospital in Botswana, in southern Africa. Sera from 466 patients were analysed. The sexually transmitted diseases (STD) group consisted of 175 women and 178 men, who consulted the STD-clinic for complaints which could be attributed to STD or infertility and the antenatal clinic (ANC) group consisted of 113 pregnant women, who attended routine ANC. Sera were analysed with HIV-ELISA, and 3% were positive. All sera were negative in Western blot and were considered false-positive in HIV-ELISA. In the STD group, 42% of the women and 39% of the men, were seropositive for syphilis, while 41% were positive in the ANC group. The figures for clinically demonstrated genital lesions were 33%, 60% and 13%, respectively. It is concluded that HIV-infection is a new disease in Botswana, and that the prevalence is still low in the rural population examined in the present survey.