Trigger tools are a useful method to screen for adverse events and have been described in pediatric inpatient, intensive care, and surgical settings. This study describes the development and experience of a trigger tool for the ambulatory setting based on a 12-month retrospective chart review. While the investigators used a 39-item trigger tool, they discovered that only nine of the triggers generated a positive predictive value of greater than 5%. The most common triggers for adverse drug events were “medication stop,” “hospitalization,” and “emergency room” visit. The authors advocate for use of their trigger approach but perhaps focusing only on the nine high-yield triggers rather than the exhaustive list. The Institute for Healthcare Improvement pioneered the development of the trigger tool approach and maintains a Web site with information on trigger tools for a variety of clinical situations.