The organization of medical care is changing more rapidly now than at any point in the last century. For decades, health care was a cottage industry: physicians practiced independently or in small groups and had arms-length relationships with hospitals, imaging and laborator y facilities, and other health care entities. Those organizations alternately competed and cooperated as part of an informal local health care system.Recent years have seen the advent of large, integrated, corporate medicine. Today, the typical US city has 3 to 4 integrated health care systems, generally anchored around large hospitals and extending to suburban areas. 1 These systems are conglomerations of hospitals, primary care and specialist physicians, outpatient facilities, and postacute care facilities. There remains a fringe of unaffiliated institutions and physicians, but the number of such institutions is declining.Why is this occurring? And who benefits from it? Three reports in this issue of JAMA examine this question. Joynt and colleagues 2 examined the question of why consolidation is occurring, focusing on the conversion of not-for-profit hospitals to for-profit status. During their study period (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010), 237 hospitals (5.2% of their sample) converted from not-for-profit to for-profit status. For each converting hospital, the authors identified up to 3 matched control hospitals based on size category, teaching status, and region. In their primary analysis, they compared clinical and economic outcomes 2 years before conversion to 2 years after conversion and used difference-in-differences models to minimize any temporary economic and clinical outcomes occurring just before the conversion and to identify changes that occurred after a reasonable period.A central finding of the study by Joynt et al was that hospitals that converted from not-for-profit to for-profit status had very poor financial performance prior to conversion. The typical converting hospital had a patient-based operating margin ([net revenue from patient care and related revenue − total operating expenses]/net revenue from patient care and related revenue) of −6.6% and a total margin ([total revenue − total costs]/total revenue), including non-patient care activities, of −1.2%. Performance at this level is clearly not sustainable. Thus, part of the rationale for conversion is to stabilize cash flow.Based on the findings of Joynt et al, hospitals converting to for-profit status were successful at this. Between 2 years before and 2 years after conversion, operating margins at converting hospitals increased by 3.2%, and total margins increased by 2.2%. Operating margins remained negative, but the hospital as a whole would break even. This improvement in margins was significantly greater for the converting hospitals than for a set of matched controls.Joynt et al were not able to determine the factors associated with cash flow improvements, but they did rule out some explanations. The authors showed that neither Medicare re...