OBJECTIVES: Different cost components (charges, costs, payments) are required to estimate the economic impact of a drug therapy on inpatient care from a hospital and a health plan (payer) perspective.  To estimate different cost and payments for acute coronary syndrome (ACS) inpatient care from different payer (hospital vs. health plan) and benefit design [Fee-for-Service (FFS) vs. Prospective Payment System (PPS)] perspectives. METHODS: ACS discharges were identified using diagnosis-related group (DRG) codes using two data sources: 1) 2008 MarketScan administrative claims for health plan payments, and 2) 2008 Healthcare Cost and Utilization Project Nationwide Inpatient Sample (NIS) for hospital charge data. Admissions were classified as myocardial infarction (MI), unstable angina (UA), percutaneous transluminal intervention (PCI), coronary artery bypass graft (CABG), and stroke.  Cost-to-charge ratios were used to estimate cost to the hospital.  MarketScan data were used to provide payments from payers based on different benefit designs (PPS, FFS, Medicare and commercial coverage).  Cost and payment components were estimated at each DRG level and for individual ACS events. RESULTS: For ACS discharges (NIS n=109,903, MarketScan n=85,962), an admission with both PCI and CABG incurred highest hospital cost/plan payment ($43,867/$65,543) and UA incurred lowest ($4,369/$5,576).  Hospital charges were consistently higher than plan payments (e.g., PCI: $52,256 vs. $22,828), whereas estimated hospital costs were consistently lower than payments (e.g., PCI: $15,902 hospital cost vs. $22,828 payments).  Medicare payments were consistently lower than commercial payments (e.g., PCI: $17,205 vs. $22,828).  Detailed charges, costs, and payments estimates for various ACS events will be presented. CONCLUSIONS: These ACS inpatient cost estimates from hospital and health plan perspectives and for different benefit designs will facilitate economic evaluations of ACS drug therapies.  The analytic approach demonstrated the feasibility and validity of using different secondary data sources to estimate inpatients costs for various payer types and benefit designs.