PIP: This review of the comparative study of health care delivery systems is limited by the idiosyncratic data base available. As with comparative research in other areas, the definition and measurement of comparable units within varying sociocultural and historical circumstances are difficult. Samples of complex entities, such as delivery systems, are only obtained with much effort and cost. In this review attention is directed to the following: theoretical considerations; the international knowledge, technology, and manpower marketplace; patterns of mortality and morbidity and national development; health care delivery systems in modern countries; the social functions of health care; population selection and health care; the comparative effects of health care delivery systems; comparative study of prepayment and capitation systems; professionalism in medicine and the organization of roles; and convergence of health care delivery systems in postindustrial society. From a sociological perspective, the locus of control of medical decision making is a critical variable in examining the implications of medical care for social life more generally. Mostly, sociologists have failed to carefully examine varying approaches to regulation in different countries, the extent to which physicians in different countries have extramedical responsibilities, and the resulting implications for society. With the growing bureaucratization of medicine and increased regulation, sociologists will increasingly direct their efforts to such issues. A major problem in the sociological investigation of comparative medical organization is the inadequacy of traditional concepts describing emerging structural arrangements and ongoing organizational processes. The conceptual approaches that fit centralized, bureaucratized organizations are poorly adapted for studying intraorganizational networks. Almost all of the research effort among sociologists has focused on the organization of the health professions and occupations and with access to and distribution of medical care. The issue of why people seek help and where they choose to bring their problems is an area where sociologists can make a distinctive contribution.