Although medication errors can result in serious patient complications or even death, a paucity of information regarding medication errors that occur in the OR exists. AORN and the US Pharmacopeia (USP) collaboratively conducted a secondary analysis of reports of medication errors that occurred in the OR. These reports were submitted to the USP via the Medmarx program. The findings will give perioperative clinicians further insight into the types and causes of medication errors that occur in the OR and will help them develop potential prevention strategies.