A new national initiative in comparative effectiveness research (CER) is part of a broad and long-term evolution toward greater reliance on scientific evidence in clinical practice and medical policy. But CER has been controversial because of its high profile in the health care reform effort, its instantiation in a prominent new national research institute, and lingering concerns that the ultimate goal of CER is to empower the government and private insurers to reduce health care costs by restricting access to expensive new medical tests and treatments. This article presents an analysis of the policy development behind CER and focuses on its potential impact on insurance coverage and payment for oncology services. By itself, CER will not solve the tension that exists between the goal of innovative, personalized care and the eroding affordability of cancer treatment in the United States. But CER does offer an important opportunity for progress. Oncologists have taken important first steps in acknowledging their responsibility for addressing cost issues; as a professional society, they should now move forward to assume leadership in the effort to integrate clinical evidence with considerations of cost effectiveness to guide clinical practice and insurer policies.