Free perforation occurred in only 7 of 702 patients with ulcerative colitis (1 percent) without toxic dilatation seen at The Mount Sinai Hospital from 1960 to 1981; however, these seven patients represented 30 percent (7 of 23) of all colonic perforations seen in patients with ulcerative colitis in our institution during the same period. Classic physical signs of peritonitis (silent, rigid abdomen and rebound tenderness) were absent in six of the seven patients, but all had a marked deterioration in general condition after perforation. Other signs included a sudden increase in severity of abdominal pain (three patients), marked abdominal distention (four patients), and a sharp decrease in frequency of bowel movements (six patients). Mortality was high (four of seven patients, 57 percent) and characterized by comparatively longer patient histories of colitis, longer current attacks, slightly greater delays between presumed perforation and operation, much higher transfusion requirements, and a 100 percent incidence of coagulopathy (thrombocytopenia and increased prothrombin time in three of four patients, and increased partial thromboplastin time in all four patients). The possibility of free perforation in ulcerative colitis must be considered in fulminating cases, even in the absence of colonic dilatation. Careful clinical monitoring and early surgical intervention may be the keys to reducing mortality.