Managed care refers to a variety of strategies and organizational arrangements used to reduce unnecessary use of health services, contain costs, and improve healthcare quality. Managed care is a countervailing power in competition with other institutions over the organization and financing of medicine. Sociologists have debated whether managed care contributed to the deprofessionalization, proletarianization, or corporatization of physicians. Public trust has historically supported the professional authority of physicians, but the rapid expansion of managed care challenged that trust. Insights gathered from the study of managed care should inform our understanding of current policy initiatives.