AIM: The availability of large clinical databases allows for careful evaluation of surgical practices, indicators of quality improvement, and cost. We used a large clinical database to compare the effect of surgeon and hospital volume for the care of children with hypertrophic pyloric stenosis (HPS). METHODS: Patients with International Classification of Diseases-9 codes for HPS and pyloromyotomy were selected from the 1994 to 2000 National Inpatient Samples database. Multiple and logistic regression models were used to evaluate the risk-adjusted association between provider volume and outcomes. RESULTS: Postoperative complications occurred in 2.71% of patients. Patients operated on by low- and intermediate-volume surgeons were more likely to have complications compared with those operated on by high-volume surgeons (95% confidence interval [CI], 1.25-3.78 and 95% CI, 1.25-2.69, respectively). Patients operated at low-volume hospitals were 1.6 times more likely to have complications compared with those operated at intermediate- or high-volume hospitals (95% CI, 1.19-2.20). Procedures performed at high-volume hospitals were less expensive than those at intermediate-volume hospitals by a margin of 910 dollars (95% CI, 443-1377 dollars). CONCLUSIONS: These data represent the largest study to date on the epidemiology, complication rate, and cost for care for HPS. Patients treated by both high-volume surgeons and at high-volume hospitals have improved outcomes at less cost.