Symptoms of irritable bowel syndrome (IBS) using the Manning Criteria were sought by a questionnaire administered to 400 (male-female ratio 3:1) apparently healthy medical students. With a response rate of 84%, 230 (65.5%) reported more than six episodes of abdominal pain in the preceding year (1992-1993). Contrary to expectation, 100 (43.5%) reported symptoms consistent with the diagnosis of IBS. The one-year period prevalence of the syndrome was 30% overall, with prevalence figures of 24% for males and 48% for females (P < 0.01). There was no difference in the type of diet (mainly high-fiber diets) consumed by subjects with and without IBS. About two thirds of the subjects with IBS had sought medical advice during the study period; the consultation behavior was influenced by factors such as the presence of other symptoms. This is the first detailed evidence in a random sample of an African population showing symptoms consistent with a diagnosis of IBS to be very common. It casts doubt on the assumption generated by other workers that IBS is rare among native Africans.