Entrepreneurship has traditionally been studied either as a set of psychological characteristics, or as a residual of environmental structures such as social networks.  Drawing upon the literature on expertise in cognitive science, psychology, and decision-making, this paper develops a detailed framework that (a) demonstrates that entrepreneurship is a form of expertise; (b) relates effectuation theory to theories of expertise in general; and, (c) formulates testable propositions for the role of effectual action in the development of entrepreneurial expertise and firm growth.