Although the idea that competencies are underlying sustainable competitive advantages is central, there has been no thorough investigation into the very nature of competencies in the strategic management literature. Theories on the sociology of knowledge are used to advance the resource-based perspective of the firm into a coherent perspective of competencies. The implications on sustainable competitive advantages are discussed, by focusing on the processes of imitation of competencies in different social contexts. It is proposed that the emergent competence-based perspective of the firm has several important implications for management research and theory building.