This chapter attempts to contribute to the psychology of organization and management by discussing a theory of entrepreneurship, its empirical base, and its implications. First, it argues that a psychology of organization is incomplete if we do not understand how organizations get started-which is usually the doing of one entrepreneur or of a group of entrepreneurs. Second, it argues that any theory of entrepreneurship should use active actions as a starting point-entrepreneurship is the epitome of an active agent in the market (rather than a reactive agent). Third, it discusses an action regulation theory to better understand the psychology of entrepreneurship. Fourth, it provides empirical work based on this theory that is supposed to help understand entrepreneurial success. Finally, a theoretically derived intervention is suggested to help entrepreneurs to be successful at growing an organization.