Preoperative colonoscopy is recommended in the evaluation of patients with lower gastrointestinal malignancies. The purpose of this study was to investigate the indications and impact on patient management in patients undergoing intraoperative endoscopy. This is a retrospective review of patient charts from February 1972 to July 1994 of 69 intraoperative endoscopic procedures performed in 54 patients during 54 operative sessions. The results of intraoperative endoscopy affected patient management in 29 of the 54 operative sessions (54%). This included 9 cases (17%) in which the planned surgical procedure was altered. There were no complications related to the endoscopies and 99% were completed successfully. Intraoperative endoscopy can provide important information that can alter the surgical management of patients with colorectal disease. This technique should be considered when intraoperative palpation fails to identify synchronous lesions identified on preoperative studies or in cases where the preoperative study is suboptimal.