The National Patient Safety Foundation (NPSF) published a report in an effort to improve the effectiveness and utility of patient safety efforts and concentrate on an objective of preventing future harm. Traditionally, the process employed to produce recommended practices to improve how we can learn about and react from adverse events and unsafe conditions has been called root cause analysis, but it has had inconsistent success. Prevention requires actions to be taken, and so NPSF has renamed the process Root Cause Analysis and Action, RCA2 (RCA “squared”) to emphasize this point. The overall purpose of this review document is to identify system vulnerabilities so that they can be eliminated or mitigated. The review is not to be used to focus on or address individual performance, since individual performance is a symptom of larger systems-based issues.