A combined retrospective (1971–1980) and prospective (1981–1990) study of the epidemiology, clinical characteristics and pathology of breast cancer in a black African population was carried out. There were 1946 biopsy-proven cases, with a rate frequency of 33.6 per 100 000 patients per year. The age range was 14-96 years but 70 per cent of patients were between 26 and 50 years old. The cumulative frequency of cancer was 0.8 per cent at age <20 years and 3.3 per cent at age <25 years: the peak age range for disease was 36–45 years. Of 1842 evaluable patients, 17.2 per cent presented with stages I or II cancer and 73.8per cent with stage III disease. The dominant histopathological type was infiltrating ductal cancer (49.2 per cent), followed by undiferentiated anaplastic carcinoma (33.3 per cent). Burkitt's lymphoma occurred in five patients and developed concurrently and rapidly during lactation in four. The prospective study did not demonstrate that age at menarche or first full-term pregnancy, duration of breast feeding or parity were risk factors in black women.