BACKGROUND Failure to reconcile medications across transitions in care is an important source of harm to patients. Little is known about medication discrepancies upon admission to skilled nursing facilities (SNFs). OBJECTIVE To describe the prevalence of, type of medications involved in, and sources of medication discrepancies upon admission to the SNF setting. DESIGN Cross-sectional study. PARTICIPANTS Patients admitted to SNF for subacute care. MEASUREMENTS Number of medication discrepancies, defined as unexplained differences among documented medication regimens, including the hospital discharge summary, patient care referral form and SNF admission orders. RESULTS Of 2,319 medications reviewed on admission, 495 (21.3%) had a medication discrepancy. At least one medication discrepancy was identified in 142 of 199 (71.4%) SNF admissions. The discharge summary and the patient care referral form did not match in 104 of 199 (52.3%) SNF admissions. Disagreement between the discharge summary and the patient care referral form accounted for 62.0% (n = 307) of all medication discrepancies. Cardiovascular agents, opioid analgesics, neuropsychiatric agents, hypoglycemics, antibiotics, and anticoagulants accounted for over 50% of all discrepant medications. CONCLUSIONS Medication discrepancies occurred in almost three out of four SNF admissions and accounted for one in five medications prescribed on admission. The discharge summary and the patient care referral forms from the discharging institution are often in disagreement. Our study findings underscore the importance of current efforts to improve the quality of inter-institutional communication.