Obtaining a best possible medication history (BPM) is an important component of successful medication reconciliation programs. This study compared the impact of a pharmacy-led medication reconciliation program including BPMH on adverse drug events (ADEs) and complications among high-risk, complex patients across 16 hospitals. In the six months following implementation, 80,000 reconciliations were completed and nearly 40% required additional medication follow-up and/or clarification. Researchers identified a statistically significant decrease in both ADEs and complications after implementation.