In cases where preoperative studies may have been inadequate or could not be performed, intraoperative endoscopy (IOE) becomes an essential investigative tool for identification of synchronous lesions, of nonpalpable lesions, of sources of bleeding, and localization of lesions during laparoscopic colonic surgery. We report our experience with IOE, and describe our techniques of transabdominal colonoscopy. A review of the IOE performed in hospitals affiliated with the University of Miami was done. Fifty-eight patients received IOE from July 1994 to August 1996. There were 47 colonoscopies (38 transanal and 9 transabdominal), and 11 flexible sigmoidoscopies. Colorectal cancer, diverticulitis, inflammatory bowel disease, and lower gastrointestinal bleeding represented 83% of cases. In 10% of cases IOE changed the extent of the surgical procedure. There were no complications related to IOE. We conclude that in selected patients undergoing colorectal procedures, IOE is an essential tool. It can be performed safely, effectively, and rapidly.