We retrospectively reviewed 137 cases of outpatient endoscopic sphincterotomy (ES) performed over a 4-year period in a single center and compared them with an equal number of inpatient ES. The indications for ES in outpatients as compared with inpatients were, respectively: choledocholithiasis, 60% and 70%; papillary stenosis, 35% and 15% (p less than 0.001); stent insertion, 3.6% and 14% (p less than 0.01); and ampullary tumor, 1.4% and 0.7%. Complications were noted within 2 to 4 hours of ES in 6.6% of outpatients, a rate similar to that of inpatients--7.3%. Outpatients with complications were immediately admitted and stayed in the hospital for a mean of 5 days. No delayed complications were noted and no deaths occurred. Thus, a policy whereby selected individuals undergo ES as outpatients, with hospitalization reserved only for those in whom a complication develops, is reasonable and safe.