Unintentional medication discrepancies during transitions in care (such as hospitalization and subsequent discharge) are very common and represent a major threat to patient safety. One solution to this problem is medication reconciliation. In response to Joint Commission requirements, most hospitals have developed medication reconciliation processes, but some have been more successful than others, and there are reports of pro-forma compliance without substantial improvements in patient safety. There is now collective experience about effective approaches to medication reconciliation, but these have yet to be consolidated, evaluated rigorously, and disseminated effectively.