Five hundred and fifty-one patients attending the Special Treatment Clinic (STC) of the University College Hospital, Ibadan, between January 1989 and July 1990 were investigated for the common sexually transmitted diseases to determine the current relative prevalence rates of these infections. The patients were also investigated for human immunodeficiency virus (HIV) infection. Of the 551 patients, 384 (69.9%) were diagnosed as having sexually transmitted diseases. The most frequent STDs were gonococcal infections, non-specific urethritis and cervicitis and the genital ulcer diseases (GUDs) with prevalence rates 25.6%, 17.8% and 12% respectively. In addition to the common STDs, HIV infection was detected in 28 (5.1%) patients. Both HIV-1 and HIV-2 were detected as follows: HIV-1 in 16 (2.9%) patients and HIV-2 in 12 (2.2%) patients. All but one of the HIV-seropositive patients also had concurrent sexually transmitted diseases.