AIM: To assess the prevalence of clinically significant lesions in patients with minimal bright red bleeding per rectum (BRBPR). METHODS: Consecutive outpatients prospectively underwent colonoscopy at Loghman Hakim Hospital, Tehran. Minimal BRBPR was defined as small amounts of red blood after wiping or in the toilet bowl. Patients with the following alarm signs were excluded: Positive personal history of colorectal neoplasms or inflamma-tory bowel disease (IBD), positive first degree family history of colorectal neoplasms, history of altered bow-el habits, recent significant weight loss, and presence of iron deficiency anemia. Neoplastic polyps, colorectal carcinoma, and IBD were defined as significant lesions. rnRESULTS: A total of 402 patients (183 female and 219 male, aged 43.6±15.7 years) were studied. Hemorrhoids (54.2%), anal fissures (14.2%) and ul-cerative colitis (14.2%) were the most common lesions and colonoscopy was normal in 8.0%. Significant le-sions were found in 121 (30.1%) patients, including 26 patients (6.5%) with adenocarcinoma and 30 (7.5%) with adenomatous polyps. Almost all patients with significant lesions had at least one lesion in the distal colon, an adenocarcinoma and an adenomatous polyp in the proximal colon were found in 2 patients with hemorrhoids. rnCONCLUSION: Flexible sigmoidoscopy appears to be sufficient for the evaluation of average risk patients with minimal BRBPR. Rigid sigmoidoscopy may be used as an altative in patients less than 40 years of age in settings where the former is not available. The choice of colonoscopy over flexible sigmoidoscopy in patients aged over 50 years should be individualized.