Toxic megacolon has rarely been reported in the course of antibiotic-induced pseudomembranous colitis. We have been able to collect 20 cases from the literature and add one new case. The mortality in the collected series was 33 per cent. The critical factor in improving survival is early recognition of the pseudomembranous colitis. Most patients can be managed medically by removal of the offending antibiotic, bowel rest, vancomycin, and steroids. If toxic megacolon develops in the face of appropriate medical management, an aggressive surgical approach is indicated, as with ulcerative colitis. Subtotal colectomy appears to be the procedure of choice.