The medical records of all patients ages 0 to 21 years who underwent proctosigmoidoscopy and/or rectal biopsy over a 27 month period of time were reviewed to determine the efficacy and safety of these procedures in pediatric patients. One hundred twenty-one patients underwent proctosigmoidoscopy; 91 of these also had rectal biopsies. Median age was two years; 21% were less than six months and 8% less than one month of age. Depth of examination was 10 to 15 cm in most patients greater than 10 years of age. Induced friability was the most frequently observed mucosal abnormality. Abnormal findings were almost always present in patients with bloody diarrhea and were quite common in those with rectal bleeding, but less common in those with chronic diarrhea and abdominal pain. Colitis of various causes was the most common cause of blood in the stool; anal fissures were found in only four of 23 patients with rectal bleeding. Both proctosigmoidoscopy and rectal biopsy were needed to exclude the presence of colitis. Mobidity was 0% with proctosigmoidoscopy and 0.34% with rectal suction biopsy.