The American Cancer Society (ACS) recommends that asymptomatic women, age 50 and over, undergo sigmoidoscopy every 3 to 5 years, after two negative yearly exams. Epidemiologic evidence suggests that women with gynecologic or breast cancers have an increased risk of developing colon cancer. It is unclear whether the ACS guidelines are applicable for women with a new diagnosis of gynecologic malignancy. This retrospective study was undertaken to assess the usefulness of preoperative colonoscopy in our gynecologic oncology patient population. Patients undergoing evaluation for a major operative procedure for known or suspected gynecologic malignancies were referred for colonoscopy at the discretion of their attending surgeon. Five hundred patients' charts were reviewed to identify 212 patients in whom preoperative colonoscopy was performed (the study group). In this group, 17 cases of colonic polyps, 5 cases of synchronous colon cancer, and 2 cases of cancer metastatic to the colon were discovered, representing 11% of the study group. Whereas 23% of the patients screened were less than 50 years of age, only two cases of polyps occurred in this age group, and no cases of cancer. Patients aged 70 or greater made up 28% of the study group, but accounted for 41% of the cases of polyps and 40% of the colon cancers. Twenty-nine percent of the study group had adenocarcinoma of the endometrium, representing 7 of 17 cases of polyps, 1 of 5 colon cancers, and 1 of 2 metastatic cancers. Although this retrospective study involved colonoscopy, the locations of the observed lesions were within the theoretic reach of a flexible sigmoidscope in 75% of cases. We conclude that in the preoperative workup of gynecologic oncology patients, no colon screening is needed in the asymptomatic patient less than 50 years of age. ACS guidelines are appropriate for patients aged 50-70, but for those 70 or greater we would consider full colonoscopy.