Computerized provider order entry (CPOE) has proven to be effective at preventing prescribing errors. However, the safety aspects of CPOE have yet to be optimized, as evidenced by studies demonstrating that CPOE systems do not always prevent incorrect orders from being entered. This study analyzed CPOE safety vulnerabilities by examining erroneous orders—medication orders identified by ordering clinicians as having been incorrect. Surveys of ordering clinicians found that erroneous orders were most often discontinued because they had been entered for the wrong patient, for the wrong medication, or were a duplicate order for a medication the patient was already taking. Erroneous orders appear to be a useful way of identifying vulnerabilities within CPOE systems, and the authors suggest that institutions should develop surveillance methods for detecting such vulnerabilities in order to optimize CPOE safety. A previous Annual Perspective discussed the impact of CPOE on patient safety.