An estimate of the incidence of diverticular disease of the colon was based on all the barium enema examinations in Edinburgh over four years (12 335 cases); using the census data for 1971, incidence rates for the city by age, sex, and electoral ward were calculated. The overall annual incidence rate was 1-55/1000, the rate rising sharply with increasing age. The incidence of diverticular disease varies from ward to ward (range 0-92-2-04/1000), adjacent wards have similar incidence rates and the six wards with the lowest rates are clustered together in the South East of the city. Ward incidence rates have a significant negative association with the percentage of owner occupiers living in that area.