The landscape of the Greek and Roman economies is invariably configured of individuals, and also of institutions, the organized activity of production and commerce. This chapter explores, within the ancient world, to what extent was economic growth fostered or impeded by the institutional and legal framework within which the Greek and Roman economies operated. The question may be at least formally addressed through modern scholarly methods associated especially with Law and Economics and with the New Institutional Economics. The chapter provides an overview of the methods themselves, and then suggests several ways in which these methods can be applied to come to a deeper understanding of economic organization and the possibilities for economic growth in the Greek and Roman worlds. Adverse selection is an example of how asymmetrical information can affect entry into a market. A cardinal implication of the Coase theorem is that markets cannot and do not exist in isolation from their institutional context.