Patients in nursing homes are generally elderly, chronically ill, and take multiple medications, which places them at higher risk for medication errors. The state of North Carolina maintains a mandatory medication error reporting system for all nursing homes. This study analyzed data from this system to characterize errors due to anticoagulant drugs (which are considered high-risk medications). Errors were found to be common and harmful, often due to inadequate monitoring to ensure appropriate drug dosing. The authors recommend several potential solutions, but any interventions will likely also have to address the fact that safety culture in nursing homes is generally poor. An AHRQ WebM&M commentary discusses a preventable error due to inadequate monitoring of the anticoagulant warfarin at a nursing home, and an AHRQ WebM&M perspective explores the difficult problem of ensuring medication safety in nursing facilities.