Background: Hematochezia is a common symptom among young persons and may be a sign of serious colonic pathology. Evaluation of the entire colon is widely recommended for persons over age 50 years with rectal bleeding. In younger patients, the appropriate recommendations are less clear. The goal of this study was to determine the prevalence of underlying disease in young persons presenting with rectal bleeding. Methods: Retrospective cross sectional study of persons under age 50 years undergoing outpatient colonoscopy (COL) or sigmoidoscopy (SIG) for hematochezia. Eligible subjects were identified from the endoscopy database at the University of Pennsylvania Health System. Persons with a known history of inflammatory bowel disease, colonic polyps, colorectal cancer, AVMs, ischemic colitis, radiation proctitis, or abnormal barium studies were excluded. Pathology reports were reviewed for all persons identified as having polyps or mass lesions. If persons underwent more than one procedure for hematochezia, only the first was considered in these analyses. Results: 570 patients (309 F / 261 M) met our inclusion criteria. Of these, 232 (41%) underwent COL and 338 (59%) underwent SIG. Persons over age 40 years were significantly more likely to undergo COL (54% vs 30%, p