Prior studies have documented that medication errors frequently occur at times of transitions in care such as hospital admission and discharge. Hospitals are now required to have a system for medication reconciliation as a means of averting such errors. This article describes the development, pilot testing, and implementation of a medication reconciliation application within the electronic medical record (EMR) of an integrated health care network. At the time of hospital admission, the system integrates data from the outpatient and inpatient EMR to formulate an accurate medication list, which is used as the basis for medication reconciliation.