This fifth issue in the Industry and Health Care series takes a quick turn through unpredictable and only partially charted waters. The series as a whole has set out to explore the role of industry as a potential agent of change in the health care system, and to map the courses that may lead toward control of costs. One that looks possible is the effort now being made to infuse some competition into the health care industry through organized systems of care, known as HMOs. Health maintenance organizations, especially the fee-for-service variety known as IPAs (individual practice associations), have been a particular inter est of the Center for Industry and Health Care, where a national data base 'on IP A performance is being established with the aid of the Robert Wood Johnson Foundation. The Center's identity with HMOs, combined with its focus on industry and health care, has afforded us unusual access to nascent corporate thinking on the pros and cons of HMO sponsorship. We are grateful for these opportunities, and for the insights industry people have shared with us. This series draws heavily on that experience.