Fiberoptic colonoscopy was performed on 15 patients 1.5-16 yr old. Ten patients were hospitalized and 5 were outpatients. Of 12 with frank or microscopic blood in stools, fiberoptic colonoscopy revealed single polyps in 6 patients, ulcerative colitis in 2 and negative results in 4 with prior nondiagnostic radiographic studies. Of 3 patients with recurrent lower abdominal pain and nondiagnostic laboratory and radiographic studies, colonoscopy revaled ulcerative colitis in 1, granulomatous colitis in 1 and negative findings in 1. Polypectomy through the colonoscope was accomplished in all 6 patients with polyps. Perforation of the sigmoid colon during polypectomy with the snare loop was the single complication encountered. Lower intestinal endoscopy should be selectively considered for diagnosis and therapy of unexplained bleeding or recurrent lower abdominal pain in children in whom proctosigmoidoscopic, laboratory and radiographic examinations do not achieve a diagnosis.