From January 1987 to December 1991, 37 patients underwent intraoperative colonoscopy for several indications; these latter can be summarized in the need to define the site or extension of the lesions treated or detected by endoscopy before surgery. This procedure is therefore necessary in those cases in whom intraoperative endoscopy is likely to be useful in planning the surgical treatment. The use of intraoperative colonoscopy should be however considered complementary, but not substitutive, of the preoperative colonoscopy.