OBJECTIVES: The role that payers play in the pharmaceutical market has been increasing in prominence.  Much research has focused on public payers and how drug reimbursement policies change in response to data from drug effectiveness studies. However, the commercial payer perspective has not been well researched. This study seeks to describe how U.S. commercial payers use different types of comparative evidence to make reimbursement and formulary placement decisions. METHODS: We recruited  20 US  commercial payers who currently participate in or lead pharmaceutical and therapeutics committees for their plans. Our participants represent managed care organizations that cover a total of more than 95 million members. We conducted semi-structured qualitative interviews comprised of five representative scenarios and asked payers to rate how they value different study designs for each scenario. The interviews were transcribed, the responses were tabulated, and then analyzed for content. RESULTS: The reported value of the study designs differed between national and regional payers as well as between medical and pharmacy directors.  National payers have more resources and are more likely to value and conduct retrospective analyses and decision modeling than regional payers. Pharmacy directors tend to favor retrospective analyses and medical directors value RCTs, pragmatic trials, and prospective non-experimental studies.  Although RCTs were often the highest ranked study design, payers still found prospective non-experimental studies and retrospective analyses valuable for certain uses.  Payers are currently unable to manage most oncology products beyond labeled indications due to political pressure to cover all drugs regardless of price. CONCLUSIONS: Payers value and utilize data from a broad range of study designs to inform formulary placement decisions. However, the disease state, market condition, and type of payer will influence what sort of comparative evidence is of the most value.