Introduction: It is difficult to predict which patients with ovarian cancer will require bowel surgery. We propose that sigmoido­scopy performed by an experienced colorectal surgeon could predict the need for bowel resection as part of optimum cytoreduction by assessment of rigidity and encasement of the rectosigmoid colon or mucosa! involvement. Laparotomy may then be performed electively in collaboration with a colorectal surgeon after administration of bowel preparation. Methods: In a prospective study 30 panents undergoing surgery for a high suspicion of ovarian malignancy and with at least two of either a complex pelvic mass on ultrasound, elevated CA125 or ascites were studied. Flexible sigmoidoscopy performed at time of admission was reported as “clear bowel”, “external compression only” or “mucosal Involvement” with the recommendation to “avoid resection” or “may need resection”. Results: Sigmoidoscopy was completed in all patients and was well tolerated. Satisfactory preparation and evaluation was possi­ble in 70% and did not delay definitive surgery. 67% (20/30) of cases proved to have ovarian carcinoma. Overall prediction to avoid resection was correct in 21/25 and to resect in 5/9 with accurate prediction in those with ovarian cancer of 17/20 cases. This included 3/4 sigmoid colectomies for ovarian malignancy as part of an optimum debulking procedure. Sigmoidoscopy was more accu­rate than relying on a history of change in bowel habit alone in predicting the need for bowel resection. Conclusions: Sigmoidoscopy was shown to be a practical procedure, causing no significant morbidity in patients with ovarian carcinoma. In evaluating a pelvic mass it can exclude primary colorectal pathology and impending obstruction. Flexible sigmoido­scopy correctly identified the majority of cases which required colorectal surgery and allowed an optimal resection to take place as a planned procedure.