The patient-centered medical home has become a prominent model for reforming the way health care is delivered to patients. The model offers a robust system of primary care combined with practice innovations and new payment methods. But scant information exists about the extent to which typical US physician practices have implemented this model and its processes of care, or about the factors associated with implementation. In this article we provide the first national data on the use of medical home processes such as chronic disease registries, nurse care managers, and systems to incorporate patient feedback, among 1,344 small and medium-size physician practices. We found that on average, practices used just one-fifth of the patient-centered medical home processes measured as part of this study. We also identify internal capabilities and external incentives associated with the greater use of medical home processes.