Recent efforts to introduce competition, consistent with microeconomic theory, into the United States health care system raise questions of distributive justice. Similarities between microeconomic theory and libertarian philosophy suggest the possibility of confusing economic goals of efficiency and cost containment with social goals of equity of access to care. This paper raises the fear that if the two are confused, society may unwittingly abandon any serious effort to ensure that the poor have access to essential types of medical care, because libertarian philosophy cannot justify placing any constraints, however beneficient, on the actual distribution of benefits and burdens of illness resulting from free trade.