What are the effects of hospital, health market, regulatory, and community characteristics on the decision to develop a physician-organization arrangement and on the type of arrangement that is selected? The Hospital Research and Educational Trust (HRET), in collaboration with the Wharton School of the University of Pennsylvania, studied joint hospital and physician group efforts to create integrated service arrangements and facilitated managed care contracting. The study provides baseline data on the prevalence of these relationships, associates different organizational arrangements with measurable characteristics to develop classification schemes, and develops an analytic framework for assessing why hospitals and physicians implement various arrangements.