Although recommended, retroflexion to evaluate the rectal vault is not always practiced in endoscopy. A prospective study of 600 consecutive patients undergoing flexible sigmoidoscopy or colonoscopy was done to evaluate whether retroflexion increased the diagnostic yield compared with straight view examination of the distal rectum and whether the findings altered subsequent patient management. In this study, 30 patients were found to have distinct lesions in the anorectum. More than 50% of lesions in the rectal vault were identified only by retroflexion. Adenomatous polyps were seen in nine patients, of which six were identified only by retroflex view. Fifty percent of patients with adenomatous polyps in the rectal vault identified only by retroflexion during screening sigmoidoscopy were found to have right sided adenomas on colonoscopy. The retroflex view produced significant additional information, compared with standard forward view of the rectum, and altered the patient management plan. The procedure was easily performed without complications and was tolerated well by patients. Unless contraindicated, rectal retroflexion should be universally practiced and emphasized in training as more nonphysicians become involved in performing sigmoidoscopy.