A variety of complications are associated with fiberoptic colonoscopy. Life-threatening complications such as perforation and hemorrhage may require surgical intervention. The records of all patients who underwent fiberoptic colonoscopy, with or without biopsy, polypectomy, electrocoagulation, or laser therapy at St. Luke's-Roosevelt Hospital Center were reviewed. Thirteen of 21 perforations occurred during polypectomy, laser therapy, or difficult diagnostic colonoscopy. Eight patients developed a perforation after an uneventful diagnostic colonoscopy. Three patients required operative control of hemorrhage following polypectomy and one after multipolar electrocoagulation (BICAP) therapy for a cecal arteriovenous malformation. Two patients had benign pneumoperitoneum and one a retained polyp snare. Of the 28 patients in this entire series, 26 underwent operative resection or repair. Seventeen (65%) of the latter group underwent primary resection or closure of perforation without protective fecal diversion. Only one (5.9%) septic complication occurred in this group. Twelve patients in the perforation group (57%) underwent primary resection with anastomosis or closure of perforation without fecal diversion. One (8.3%) developed a septic complication. In this entire series, four deaths (14.3%) occurred, all of which were in the perforation group. Delay in diagnosis of perforation was the main factor contributing to death. No patient died of hemorrhage, benign pneumoperitoneum, or retained polyp snare. The key to successful outcome in perforation is early diagnosis and prompt operative intervention.