The purpose of this article is to build a coherent framework of the four main theories relating to the internationalization of firms, in order to facilitate better business teaching and research. Yet, theories of the internationalization of firms are broad and rest on different underlying assumptions. With the purpose of clarifying the potential for integration of partial theories and fragments in a more logically connected theoretical area, this article offers a meta-theoretical overview of four perspectives within international business economics: Research and its related background, basic assumptions, study area, and implications of the theories in the internationalization of the firm. (Contains 1 figure and 3 tables.)