Patients (N = 2,097) undergoing ambulatory office colonoscopy were followed to determine the incidence of endoscopic complications. In this group, 1,320 patients had diagnostic colonoscopy with or without biopsy; 777 patients had 2,019 polyps removed. Three of 2,097 patients (0.1%) had transient hypotension requiring i.v. fluid resuscitation and oxygen administration. All patients went home without sequelae. Acute postpolypectomy bleeding occurred in 11 of 777 patients (1%) requiring acute management; bleeding was controlled during colonoscopy in all. Postpolypectomy syndrome occurred in 15 of 777 patients (1%). All patients were treated medically. Late postpolypectomy bleeding occurred in 15 of 777 patients (2%). Perforation occurred in two of 777 patients (0.3%), at 1 and 9 days postpolypectomy. Both patients underwent surgery with uneventful recoveries. We conclude that office colonoscopy inclucing polypectomy is safe. The overall complication rate for therapeutic ambulatory colonoscopy was 5%, with major events requiring hospitalization in 2% of patients.