In 280 unselected necropsies on patients over 20 years of age in Northern Norway, diverticular disease was present in 25% of the males and 43% of the females. The frequency of diverticular disease increased in both sexes by age. Both the frequency of diverticular disease and the average number of diverticula per case with diverticular disease were higher in females than in males in all age groups. The sigmoid was the most frequent site of diverticula in both sexes and for all ages, and the average number of diverticula per diverticulum-bearing segment was also highest in the sigmoid for all ages and in both sexes. The average number of diverticula in the sigmoid of affected individuals increased with age and with the number of segments involved. Diverticular disease was not associated with adenomas of the large intestine or with malignant or benign neoplasms elsewhere in the body or with any of the common diseases thought to be related to a Western type of diet, except with cerebrovascular disease.