Ulcerative colitis is reported to be rare in black populations of sub-Saharan Africa. This series of the first 46 patients treated at Baragwanath Hospital, Soweto, indicates that most patients (72%) presented with severe symptoms and extensive colonic involvement. There is a paradox of severe extensive disease yet relative lack of complications requiring surgery. This is probably due to the modification of the natural history of the disease through medical treatment, particularly corticosteroid therapy. There is a long delay between onset of symptoms and diagnosis (3 years). Ulcerative colitis affects mainly women. The mean age of presentation is 36 years. Patients are urbanized and most belong to the upper educational group while a significant proportion are in the higher occupational categories. Follow-up is poor with only one third of patients regularly attending the out-patients department once the disease is controlled.