This paper examines the relationship between firm behavior (in terms of basic strategies and organization) and tecbnological regimes (defined in terms of opportunity, appropriability and cumulativeness conditions, and of the complexity of the knowledge base). This paper advances two major points. First, technological regimes define broad prescriptions and trade-offs which identify the basic dynamic mechanisms and viable firm behavior. Second, the menus of viable technology strategies and organizations of innovative activities increas the higher and the more pervasive are technological opportunities, the higher is the degree of cumulativeness of technical change, the lower is the degree of appropriability of innovations and the more complex is the relevant knowledge base. These points are illustrated with evidence from the semiconductor, biotechnology and computer industries