Close followers of the evolution of the Series on Industry and Health Care will recognize in this fourth volume some continuity and some change. The essential concept behind the series remains: here, as before, we are looking to private industry as a potential agent of change in the American health care delivery system. We have made some structural accommodations, however, to comments received from readers in industry and in health services. The original concept of a topical monograph supplemented by a separate hardbound volume of background papers has yielded to the present formula in which each volume is complete in itself. The series continues to draw much of its material from interdisciplinary working conferences convened by the Bos ton University Center for Industry and Health Care. Rather than publish confer ence proceedings, we have again undertaken to analyze the discussions and to integrate with them some timely background materials. Readers have found this format a major improvement over traditional conference reports and sum maries.