The Health Policy Institute of Boston University, with the assistance and full cooperation of HealthStop--the nation's third largest chain of investor-owned, freestanding ambulatory care centers (IFAC's)--propose to conduct an indepth case study of the HealthStop system of 20 centers. HealthStop's niche in the ambulatory health care system will be defined; issues of pricing, access, and parameters of quality will be investigated; preliminary hypotheses will be tested; and future research questions honed. This extensive and intensive exploration of HealthStop will provide basic and baseline data on a fast-growing new component of the ambulatory care delivery system. The objectives are to describe the HealthStop system, quantitatively and qualitatively, in full and accurate detail, to investigate the impact of various financing arrangements on service delivery patterns, to explore the nature and extent of local area responses to this new delivery mode, and to cast findings in a context that considers the public policy and regulatory implications of IFAC's at the state and federal level. Full access to HealthStop's database and management information has been assured. The description and analysis of HealthStop will include characteristics of patients served and not served, patient satisfaction, content and vulume of services provided, substitution vs. addition of services, structure and process indicators of quality of care, physician profiles, financial incentives and physician practice patterns, staffing and operating methods, hospital relationships and their impact on service delivery and revenue, and access to and use of venture capital. These issues will be investigated by obtaining and analyzing data regularly collected by HealthStop, and by acquiring and analyzing new information through patient, provider and investor surveys; medical chart reviews; and interviews with corporate management and regulators. The overall purpose is to provide policy makers, payers, other providers and the public with objective findings and analysis of HealthStop and its larger implications. This is intended to facilitate informed debate about a new, fast-growing and poorly understood segement of the ambulatory healthcare delivery system.