INTRODUCTION: Surgical site infection is very uncommon after pyloromyotomy in children, and it is considered a "clean" procedure under the traditional wound classification system. This study aims to investigate prophylactic antibiotic administration for pyloromyotomy among children's hospitals in the USA. METHODS: The Pediatric Health Information System (PHIS) database was retrospectively reviewed from 2014 to 2015 including all patients less than 1 year old who had a principal diagnosis of pyloric stenosis and underwent pyloromyotomy. Patient demographics, hospital length of stay, and perioperative antibiotic administration were extracted. RESULTS: A total of 4206 patients met study criteria. Most patients were male (84%) and Caucasian (70%). The median age at admission was 32 days (IQR 24-44 days), and median length of stay was 2 days (IQR 1-2 days). Antibiotics were administered perioperatively in 2153 (51%) patients with marked variation among children's hospitals. Antibiotics were given to more than 10% of patients in more than 90% of hospitals, and only two of 49 hospitals gave no antibiotic prophylaxis. CONCLUSIONS: This study has shown that at several tertiary-level children's hospitals in the USA, antibiotic prophylaxis is administered for pyloromyotomy, a "clean" procedure. This highlights the need for standardization of care and more effective antibiotic stewardship in pediatric surgery.