Medication reconciliation represents an active effort of hospitals across the country to comply with recent additions to JCAHO's National Patient Safety Goals. Using data captured from USP's Medmarx program, this study discusses the errors that resulted after implementing a medication reconciliation process. Based on analysis of more than 2000 reconciliation-related errors, the author presents the distribution of errors by category (eg, potential error, intercepted error), types of errors (eg, improper dose, wrong drug, wrong time), and leading causes and contributing factors. The author also provides case examples for reconciliation errors at admission, transfer of care, and discharge. A past study also discussed practical strategies for implementing medication reconciliation processes.