Health disparities, also known as health inequities, are systematic and potentially remediable differences in one or more aspects of health across population groups defined socially, economically, demographically, or geographically. This topic has been the subject of research stretching back at least decades. Reports and studies have delved into how inequities develop in different societies and, with particular regard to health services, in access to and financing of health systems. In this review, we consider empirical studies from the United States and elsewhere, and we focus on how one aspect of health systems, clinical care, contributes to maintaining systematic differences in health across population groups characterized by social disadvantage. We consider inequities in clinical care and the policies that influence them. We develop a framework for considering the structural and behavioral components of clinical care and review the existing literature for evidence that is likely to be generalizable across health systems over time. Starting with the assumption that health services, as one aspect of social services, ought to enhance equity in health care, we conclude with a discussion of threats to that role and what might be done about them.