This cross-sectional study was carried out among male outpatients with symptoms of STDs at the STD reference centre at the Institute of Social Hygiene (IHS), Dakar, Senegal, from March 1989 through May 1991. This study was used to determine the prevalence of STDs and HIV among male patients attending an STD clinic and to identify their socio-demographic characteristics and risk factors. A total of 975 patients were enrolled in the study. The most common syndromes were urethritis (76%) and genital ulcers (22%). Considering single infections, the major STD agents were Neisseria gonorrheae (N.gonorrheae, 30%), Chlamydia trachomatis (C.trachomatis, 15%), Treponema pallidum (T.pallidum, 12%), and Haemophilus ducreyi (H.ducreyi, 7%). HIV prevalence was 2.6 percent (25/975). After multivariate analysis, the risk factors associated with HIV infection were a history of sex with prostitutes (odds ratio [OR] = 8.6, 95% confidence interval [CI] = 2.0-37.8), unprotected sexual contact (OR = 5.6, 95% CI = 1.2-25.0), a history of urethritis (OR = 3.4, 95% CI = 1.3-8.9), current STDs due to H.ducreyi or T.pallidum (OR = 6.1, 95% CI = 2-18.8), and mixed STD infection (OR = 5.3, 95% CI = 1.3-21.8). HIV prevalence was quite low in this population compared to similar studies of STD patients from other sub-Saharan African countries. Neisseria gonorrheae and Chlamydia trachomatis were the leading causes of STDs. A history of risky sexual behaviour, previous STDs, current genital ulcers, and mixed STD infections were associated with HIV infection. Further studies are necessary to determine changes in the relationship of STDs and HIV infection in this population.