This paper concerns the technological determinants of entrepreneurial behaviour. By applying a typology of technological regimes, which describes the nature of the technological environment in which firms operate, this paper examines the sources and obstacles to entrepreneurial entry related to the process of technical change. Two major points are suggested. First, innovation in technologies of high or increasing opportunities is not always associated with entrepreneurial behaviour, but can enhance the competitive advantage of existing firms. Second, opportunities for entrepreneurship are shaped by the nature of knowledge underlying different technologies. These points are illustrated using U.S. patent statistics classified by technical field and sector of firm's principal product activity.