There is considerable enthusiasm among physicians and payers for the patient-centered medical home (PCMH) as a model of primary care that can provide better quality of care, improve the patient experience, prevent avoidable emergency room use and hospitalizations, and reduce total costs of care. But little is known about how much it costs physician practices to implement and sustain components of the medical home. This project will define incremental costs and payment options associated with the implementation and operation of a PCMH. With this information, physicians, insurers, and policymakers will be in a better position to make key decisions with regard to implementing the medical home model, compensating providers for their comprehensive services, and recognizing and promoting the PCMH as the new standard of primary care. The American College of Physicians will provide cofunding.