The contemporary expansion of investor-owned health care facilities has stimulated much controversy but little response from policymakers. We believe this results from the apparently ambiguous relationship between ownership and socially valued outcomes. In our assessment, this ambiguity occurs largely because the effects of ownership are mediated in complex ways by characteristics of the services being delivered and the training of health care providers. Reviewing both the history and current performance of nonprofit and for-profit health care facilities, we identify some of the more important of these mediating factors. Taking these into account, there is a consistent influence of ownership on the delivery of health services. On the basis of this analysis, we discuss appropriate policy responses to the future growth of investor-owned health care organizations.