In order to detect accompanying gastric lesions, we examined 22 patients with familial adenomatosis of the colon belonging to 14 families. Various gastric lesions were confirmed in 15 patients (68.2 per cent) belonging to 13 families. The lesions were found histologically to be adenoma in nine cases, fundic gland polyposis in six, carcinoma in three, and microcarcinoid in two. Fundic gland polyposis consisting of simple hyperplasia of the fundic glands seems to be the gastric lesion specific to familial adenomatosis of the colon and rectum. Familial adenomatosis coli not only affects the colon and rectum, but is also capable of inducing tumorigenicity in other organs. The stomach is one of the organs in which extracolonic lesions occur.