The diagnosis and management of dilatation of the colon and free intestinal perforation in inflammatory or infective bowel disease are reviewed with reference to 32 cases seen during an 8-year period. Toxic dilatation of the colon occurred in 20 patients, including 6 with infective colitis. Ileostomy with subtotal colectomy and mucous fistula is a satisfactory operation for toxic dilatation due to inflammatory bowel disease. Patients with infective colitis can generally be treated without operation. Free intestinal perforation was seen in 12 patients. Colonic perforation may occur in association with toxic dilatation, but more usually it occurs without dilatation as a complication of Crohn's disease. Free perforation of the ileum was seen after a short illness in patients with Crohn's disease.