OBJECTIVES: As US cost-containment pressures intensify, the hurdles to justify new drugs continues to grow.  Safety and efficacy data from clinical trials alone are no longer adequate to meet the needs of all health care decision makers driving a need for robust, complementary data.  The perceived need to collect real-world clinical, patient-centered, and/or economic outcomes through observational studies varies across stakeholders, organizations and geographical regions.  To better understand how decision makers use observational studies to inform reimbursement decisions and/or market access for new health care products. METHODS: We conducted desktop research of published literature, HTA reports and third party websites, to identify types of observational studies most valuable to health insurance and managed care organizations in reimbursement decision making. We conducted initial one-on-one interviews with payer decision makers from the RTI-HS US Commercial Payer Advisory Panel. Further interviews with current medical directors and pharmacy directors are planned to review the need for real world evidence and provide insights into decision making process. Participants will be recruited to ensure representation from organizations of different sizes, types and geographical presence to identify the specific evidence requirements and design attributes most accepted by payers, and to understand how real world evidence contributes to the value of a new drug from the payers’ perspective. RESULTS: Data from observational studies are used to describe patient segments, understand treatment patterns, resource utilization and provide effectiveness data supplementing clinical trials data. Preliminary results indicate these data help inform payer decision making but the validity and robustness of the results is often scrutinized. CONCLUSIONS: Publication of observational data in Tier 1, peer-reviewed journals lends critical credibility to real world studies. As reimbursement decision makers continue to rigorously review new  therapies, accurate and generalizable real world data will become particularly important for outcomes- or performance-based access schemes and budget management