The increasing incidence of perforated duodenal ulcer among Black patients admitted to the Johannesburg General Hospital between 1966 and 1976 is described against a background of the different forms of peptic ulcer disease seen in this hospital population. Admission for perforation during the years 1973-6 was as common among Black as among White patients. Perforation occurred principally in young (20-40 years) Black males (sex ratio 14 : 1), with a short history of preceding symptoms, and treatment was usually by simple closure. In the White group the age range was broader (20-70 years) and the male : female ratio only 2.7 : 1. Duodenal ulcer occurred predominantly in males (ratio 6 : 1), and the spectrum of the disease among the Black population in this urban environment resembled that among the White population in Johannesburg and in Western countries in the relative frequency of perforation and haemorrhage, rarity of stenosis and ratio of duodenal to gastric ulceration.