Efforts to support and use comparative effectiveness research (CER), some more successful than others, have been promulgated at various times over the last forty years. Following a resurgence of interest in CER, recent health care reforms provided substantial support to strengthen its role in US health care. While CER has generally captured bipartisan support, detractors have raised concerns that it will be used to ration services and heighten government control over health care. Such concerns almost derailed the initiative during passage of the health care reform legislation and are still present today. Given recent investments in CER and the debates surrounding its development, the time is ripe to reflect on past efforts to introduce CER in the United States. This article examines previous initiatives, highlighting their prescribed role in US health care, the reasons for their success or failure, and the political lessons learned. Current CER initiatives have corrected for many of the pitfalls experienced by previous efforts. However, past experiences point to a number of issues that must still be addressed to ensure the long-term success and sustainability of CER, including adopting realistic aims about its impact, demonstrating the impact of Patient-Centered Outcomes Research Institute (PCORI) and communicating the benefits of CER, and maintaining strong political and stakeholder support.