Twenty-five patients with adenomatosis coli were subjected to operations, and two in which desmoid tumors appeared after the operation on familial adenomatosis coli are described here. These patients were 26 and 37 year-old males. After the total colorectomy, each tumor was associated with soreness and was palpated in the lower abdominal wall, and operations were performed. The histological findings from the resected specimens, 12 cm and 34 cm in size, indicated desmoid tumors. Poliposis of the large intestine with desmoid tumors, as a complication, has been reported in 23 previous cases in Japan.