This pre-post study examines the effects of the 2003 ACGME duty hours reform on medication errors among hospitalized surgical patients. The authors hypothesized that the increase in handoffs and a changing attitude toward work—also referred to as a shift-work mentality—might lead to an increase in medication errors. Using the Nationwide Inpatient Sample, a representative sample of hospitalizations maintained by AHRQ's Healthcare Cost and Utilization Project, investigators compared medication error rates for surgical patients between 2000–2003 versus 2003–2011, accounting for trends over time and patient and hospital level covariates. Error rates for teaching hospitals were higher than expected based on patient and hospital characteristics, leading the researchers to conclude that duty hour reform increased medication errors. The magnitude of the effect was modest, and only reached statistical significance for 2 of the 8 years they examined. The effects of duty hours on safety remain controversial, without a clear consensus.