Patients who have been hospitalized often experience care coordination problems that worsen outcomes and increase costs. One reason is that hospital care and ambulatory care are often provided by different physicians. However, interventions to improve care coordination for hospitalized patients have not consistently improved outcomes and generally have not reduced costs. We describe the rationale for the Comprehensive Care Physician model, in which physicians focus their practice on patients at increased risk of hospitalization so that they can provide both inpatient and outpatient care to their patients. We also describe the design and implementation of a study supported by the Center for Medicare and Medicaid Innovation to assess the model’s effects on costs and outcomes. Evidence concerning the effectiveness of the program is expected by 2016. If the program is found to be effective, the next steps will be to assess the durability of its benefits and the model’s potential for dissemination; evidence to the contrary will provide insights into how to alter the program to address sources of failure.