Like most egalitarian political philosophers, John Rawls believes that a just society will rely on markets and business firms for much of its economic activity—despite acknowledging that market systems will tend to create very unequal distributions of goods, opportunities, power, and status. Rawls himself remains one of the few contemporary political philosophers to explore at any length the way an egalitarian theory of justice might deal with fundamental options in political economy. This article examines his arguments and conclusions on these topics. It argues that contemporary Rawlsians will reach different conclusions if they take more seriously than Rawls himself did: (1) the implications, for the political culture and the democratic regulatory state, of large firms competing in adversarial markets characterized by the inevitable “fact of market failure,” and (2) the relevance of ownership and governance relationships involving different kinds of business firms. And with respect to the second point, Rawlsians and other egalitarians have much to learn from contemporary economic, legal, and sociological theories of the firm, and the role of these theories in the structure of and rationale for corporate law. This is the kind of social theory that Rawls believes is relevant to the justification and application of theories of justice, but he himself did not appeal to it in his writings on political economy. Contemporary egalitarians can and should appeal to it now, and in doing so correct errors and omissions in Rawls’s analysis. But taking seriously the two points mentioned above will also force egalitarians who support efficient markets to face difficult dilemmas or compromises of their own.