The need for innovations in care delivery is recognized by providers, payers, and patients alike. Hospitals, physicians, and other clinicians are experimenting with new models of care designed to better meet patients' needs, reduce administrative burdens, and lower costs. The Affordable Care Act placed the Medicare and Medicaid programs at the center of a national effort to experiment with delivery and payment models designed to improve care and contain costs. These public-sector efforts have often aligned with private initiatives, such as the use of reference pricing-in which an insurer will only pay for a service at the price available from the lowest-cost provider. Employers in the public and private sectors have adopted value-based insurance design, in which copayments and deductibles are calibrated to the clinical benefit obtained from different services. Patients have the most to gain-or lose-from delivery innovations. Better, more efficient care should translate into better health and lower costs, but payment models designed to encourage innovation may have the unintended effect of limiting access to care.