Medication-related adverse events (MRE) occur frequently during anesthesia care and more research into preventing them is needed. This article presents a descriptive analysis of the MRE reported to the Spanish Anaesthesia Incident Reporting System database during the decade from 2008 through 2017. Of the 1970 MRE identified, the highest number (42%) occurred during the administration phase, and a greater percentage of administration-related MRE resulted in harm to patients (44% as opposed to 31% over all 1,970 events). The authors identified patterns and specific causes of MRE that they suggest could be mitigated using proven systems solutions.