Trigger tools are widely used as a means of detecting adverse events, but most of the existing triggers were developed and validated in adult populations. This study reports on the validation of a trigger tool for hospitalized pediatric patients, based on the Institute for Healthcare Improvement's Global Trigger Tool. In a retrospective chart review across six academic children's hospitals, the tool identified harm in 40% of admissions—a proportion comparable to a similar study in adult inpatients. Nearly half of these incidents were considered preventable. Other studies using slightly different pediatric trigger tools have found a lower incidence of adverse events. The use of trigger tools was discussed in a previous AHRQ WebM&M perspective.