INTRODUCTION: Abdominal compartment syndrome (ACS) is a problem across all critical care scenarios and is associated with a high mortality. It has not been well described in pediatric populations. OBJECTIVE: To describe the occurrence of ACS in a subset of critically ill pediatric patients and determine its effects on mortality and length of pediatric intensive care stay (PICU LOS). We also aimed to find predictors of mortality and development of ACS. SETTING: 25 bed tertiary pediatric intensive care unit. PATIENTS: Patients less than 50 kg on mechanical ventilation and a urethral catheter. MEASUREMENTS: Intra-abdominal pressures (IAP) were monitored using the intra-vesical technique. ACS was defined as IAP of >12mmHg associated with new organ dysfunction or failure. Demographics, physiologic measures of organ dysfunction, PICU LOS and mortality were monitored. MAIN RESULTS: 14 (4.7%) of 294 eligible patients had ACS. Mortality was 50% among those with ACS versus 8.2% without (p17 were predictive of developing ACS. CONCLUSIONS: ACS is a clinical problem that increases the risk of mortality in critically ill children. IAP and PRISM scores may help identify children likely to develop ACS.