Gastrointestinal endoscopy is a remarkably safe set of diagnostic and therapeutic techniques, and yet a small number of significant complications and adverse events are expected. Serious complications may have a material effect on the patient's health and well-being. They need to be anticipated and prevented if possible and managed effectively when identified. When complications occur they need to be discussed frankly with patients and their families. Informed consent, prevention, early detection, reporting, and systems improvement are critical aspects of effective complication management. Optimal complication management may improve patient satisfaction and outcome, as well as preserving the reputation and confidence of the endoscopist, and may minimize litigation.