Class of 2006 Abstract / Objectives: To assess the accuracy of medication histories taken upon hospital admission. Methods: This study was a prospective chart review comparing the accuracy of hospital admission medication histories with outpatient pharmacy and physician records. Eleven hundred patients admitted to El Dorado Hospital were eligible for participation. Patients were excluded if they were: under 18 years old, non-English speaking, in a room with precautions, transferred from a hospital or skilled nursing facility, unable to give oral consent, or admitted to a geri-psychiatric unit. After verification of medication, dose, and schedule with outpatient pharmacy and physician records, the findings were documented as perfect agreement, error of omission, or error of commission. Results: One hundred and nineteen patient histories were analyzed. Forty three patients (36%) had at least one error in their medication history. Of the 582 medications verified for accuracy, 491 medications were accurate and 91 errors were identified. Of the errors identified, 64 were errors of commission and 27 were errors of omission. The average age of patients who had at least one error type was 74.9 years, and the average age of patients who did not have any errors was 68.3 years (p = 0.004). Medication histories with six or more medications were more commonly associated with errors (p = 0.001). There was no relationship between medication history errors and specific classes of medications such as cardiovascular, lipid-lowering, and antidiabetic agents. Conclusions: Medication histories for patients older than 75 years or those that contain six or more medications are more likely to contain an error. There appears to be no link between medication class and occurrence of error. While this study does not address methods to reduce error rates, verification of medication histories with outpatient pharmacies and physicians may help reduce hospital medication errors and promote positive health outcomes.