OBJECTIVES: Selection of relevant patient safety interventions for the pediatric intensive care (PICU) requires identification of the types and severity of adverse events (AEs) and adverse drug events (ADEs) that occur in this setting. The study's objectives were to: 1) determine the rates of AEs/ADEs, including types, severity, and preventability, in PICU patients; 2) identify population characteristics associated with increased risk of AEs/ADEs; 3) develop and test a PICU specific trigger tool to facilitate identification of AEs/ADEs. DESIGN, SETTING, PATIENTS: Retrospective, cross-sectional, randomized review of 734 patient records who were discharged from 15 U.S. PICUs between September and December 2005. INTERVENTION: A novel PICU-focused trigger tool for AE/ADE detection. MEASUREMENTS AND RESULTS: Sixty-two percent of PICU patients had at least one AE. A total of 1488 AEs, including 256 ADEs, were identified. This translates to a rate of 28.6 AEs and 4.9 ADEs per 100 patient-days. The most common types of AEs were catheter complications, uncontrolled pain, and endotracheal tube malposition. Ten percent of AEs were classified as life-threatening or permanent; 45% were deemed preventable. Higher adjusted rates of AEs were found in surgical patients (p = .02), patients intubated at some point during their PICU stay (p = .002), and patients who died (p < .001). Surgical patients had higher preventable adjusted AE (p = .01) and ADE rates (p = .02). The adjusted cumulative risk of an AE per PICU day was 5.3% and 1.6% for an ADE alone. There was a 4% increase in adjusted ADEs rates for every year increase in age. CONCLUSIONS: AEs and ADEs occur frequently in the PICU setting. These data provide areas of focus for evidence-based prevention strategies to decrease the substantial risk to this vulnerable pediatric population.