During 1999, a survey of dermatological outpatients was undertaken in the five academic hospitals serving the public sector in the Johannesburg area. The relative frequency of dermatological diseases was calculated as the percentage of new dermatological outpatients. A total of 7029 patients was surveyed of whom 5355 (76.1%) were black, 770 (10.9%) white, 474 (6.7%) Indian and 430 (6.1%) coloured (mixed race). Eczema was the commonest disease accounting for one-third of all diagnoses in the total population surveyed. In black patients the commonest skin diseases were eczema (32.7%), acne (17.5%) and superficial fungal infections (5.7%). In white patients the commonest skin diseases were benign skin tumours (29.7%), eczema (17.8%) and malignant tumours (15%). In Indian patients the commonest skin diseases were eczema (30.4%), superficial fungal infections (11.8%) and psoriasis (9.6%) and in coloured patients the commonest skin diseases were eczema (34.5%), acne (13.9%) and warts (8.1%). The prevalence of seborrhoeic dermatitis, Kaposi's sarcoma and herpes zoster has increased markedly since the last South African survey in 1982. This increase may be ascribed to the epidemic of HIV infection, first diagnosed in South Africa in 1982.