BACKGROUND Medication errors lead to morbidity and mortality among emergency department (ED) patients. An inaccurate medication history is one of the underlying causes of these errors. OBJECTIVE This study was performed to determine the prevalence of patients with discrepancies between the medical list information contained in the clinical history compiled on admission to the ED and the list of medications patients are actually taking, to characterize the discrepancies found, and to analyze whether certain factors are associated with the risk of discrepancies. METHODS We conducted a cross-sectional, descriptive, observational, multicenter study with an analytic component in the EDs of 11 hospitals in Spain. We compared pharmacist-obtained medication lists (PML) with ED-obtained medication lists (EDML). Discrepancy was defined as one or more differences (in drug or dosage or route of administration) between the EDML and PML. The endpoints were the proportion of patients with discrepancies in their home medical lists, and the prevalence of certain factors among patients with discrepancies and those without. RESULTS We detected 1476 discrepancies in 387 patients; no discrepancies were found in 20.7%. The most frequent discrepancies involved incomplete information (44.2%) and omission (41.8%). In the bivariate analysis, age, number of medications, and Charlson comorbidity score were significantly associated with discrepancy. In the multivariate analysis, number of medications and hospital were the variables associated with discrepancy. CONCLUSIONS The EDML differed from the list of medications patients were actually taking in 79.3% of cases. Incomplete information and omission were the most frequent discrepancies. Age, number of medications, and comorbidities were related to the risk of discrepancies.