Of 402 United States owners of side-viewing duodenoscopes surveyed, 222 (55%) responded, reporting 10,435 endoscopic retrograde cholangiopancreatograms. Procedure failed occurred in 30%, complications in 3%, and death in 0.2%. Complications included pancreatitis, cholangitis, pancreatic sepsis, instrumental injury to the gastrointestinal tract, and drug reactions. Pancreatitis was associated with injection into the pancreatic duct, sepsis with injection into an obstructed duct or pseudocyst, and injury with abnormal gastroduodenal anatomy. Experienced workers had a 15% incidence of complications, whereas inexperience gave 4 times the failures (62%) and twice the complications (7%). The causes of complications and their prevention are discussed.