The hemolytic-uremic syndrome consists of hemolytic anemia, renal failure, and thrombocytopenia. Submucosal hemorrhage with "thumbprinting" on roentgenographic examination of the colon with barium was demonstrated in four patients, prolapse of the rectum in two patients, and pseudomembranous enterocolitis and toxic megacolon in one. These lesions are not generally associated with hemolytic-uremic syndrome. The presence of these lesions in a child with bloody diarrhea should suggest hemolytic-uremic syndrome as a possible diagnosis. Sigmoidoscopy and roentgenographic examination of the colon with barium should be done in selected patients with hemolytic-uremic syndrome to evaluate the degree of colonic involvement and the need for surgery.