OBJECTIVE: The aim of this study is to understand the human factors associated with hospital errors to provide a framework to discuss why errors occur. BACKGROUND: Patient safety in hospitals has been a major focus in healthcare for the past 15 years. Errors still occur at an alarming rate. METHODS: A cross-sectional survey of 393 hospital-based registered nurses provided perceptions of 24 items relating to human errors in hospitals. Errors were assessed for likelihood, intervenability, importance, and common occurrence. RESULTS: Data revealed 4 themes that explained 55% of the variance in likelihood to cause an error: loss of focus, unhealthy environment, interpersonal deficits, and overwhelmed. Feeling swamped was most important but was not seen as intervenable. CONCLUSION: Managers must provide a way for nurses to feel empowered to intervene on error situations they believe are most likely, common, and important.