I propose a discrete choice model of technological competition that focuses on network externalities and social interactions. This study is motivated by the importance that factors other than prices and performance have on technological change. First I study the dynamics of agents behaviours and technology shares in the hypothesis of naive and adaptive expectations. Then I assume rational expectations and study the economic implications of multiple equilibria. Finally I consider an econometric implementation, addressing the empirical issue of identification of social interactions. One application of the model is the case of polluting technologies. In a competition between “dirty” and “clean” technologies, social interactions are important in designing incentives for agents’ choice that may trigger a coordination towards less polluting scenarios.