This report summarizes research conducted by The RAND Corporation to assess the feasibility and desirability of a Health Enrollment System (HES) for the Department of Defense health care system. At the present time there are two parallel systems: one for active duty persons and one for nonactive duty persons and civilians. A potential restructuring of this system has been proposed: the Health Enrollment System. Under this plan each Military Treatment Facility would be responsible for providing care for a fixed set of persons, including all active duty persons in their catchment areas and any remaining nonactive duty persons choosing to enroll, until the enrollment target was reached. The report discusses how this system would work, insurance and health benefits in an HES, the enrollment system, setting enrollment targets, issues affecting the desirability of an HES, and the dimensions of an HES demonstration.