Between July 2002 and July 2004, all male patients (n=307) presenting to a sexually transmitted disease (STD) clinic who reported unprotected sex were enrolled in the study. Of these, 63 (20.5%), 19 (6.2%) and one (0.3%) were infected with one, two and three pathogens, respectively. The prevalences of chlamydial infection, gonorrhoea, syphilis, human immunodeficiency virus infection and trichomoniasis were 14.3%, 10.1%, 6.8%, 2.2% and 0%, respectively. The sensitivities of urethral discharge syndrome for detection of chlamydial, gonococcal, and combined forms of infection were 31.8%, 58.5% and 70.0%, respectively, with specificities of 93.5%, 97.1% and 93.9%, respectively. Positive predictive values (PPVs) were 56.0%, 68.0% and 28.0% for chlamydial and gonococcal infections and combinations of the two forms, respectively. In contrast, the sensitivity of genital ulceration syndrome for syphilis detection was only 38.0%, although the specificity was 82.5%, and the PPV was 32.0%. To reduce the number of false-positive results for STD patients who practise unprotected sex, incorporation of risk assessment and rapid diagnostic tests are recommended.