In 1988, 1233 prostitutes from different geographic areas of Kinshasa participated in a cross-sectional survey on HIV infection and other sexually transmitted diseases (STDs). Despite relatively good knowledge about AIDS and STDs, the reported preventive behaviour was poor. Only 12% of the women reported regular use of condoms, while greater than 50% of the women reported regular use of antibiotics and 38% reported doing nothing specific to prevent STDs. Thirty-five per cent of the women were HIV-positive compared with 27% in a similar survey in Kinshasa in 1986. The prevalence of other STDs was very high, ranging from 5% for genital ulcer disease (GUD) to 23% for gonococcal infection. HIV-positive women were older than HIV-negative women (26.9 versus 25.4 years; P less than 0.001), had a significantly lower level of reported condom use (9 versus 14%, P = 0.009), and reported more frequent use of antibiotics to prevent STDs (55 versus 42%, P = less than 0.001). The prevalence of syphilis, gonorrhoea, chlamydial infection and trichomoniasis was not higher in HIV-positive women compared with HIV-negative women. However, HIV-positive women had a higher prevalence of GUD (9 versus 3%, P less than 0.001), antibodies against Haemophilus ducreyi (82 versus 57%, P less than 0.001), antibodies against herpes simplex virus type 2 (96 versus 76%, P less than 0.001), condylomata accuminata (5 versus 1%, P = 0.003) and cytologic evidence of human papilloma virus on Papaniclaou cervical smear (11 versus 5%, P = 0.006). This study confirms the high incidence of HIV and other STDs among prostitutes in Africa.(ABSTRACT TRUNCATED AT 250 WORDS)