The relationship between social capital and firm activities is becoming object of growing interest in the organizations and economic sociology disciplines.  The research project we propose studies the effects of social capital on the innovation and internationalization of firm capabilities.  Our study focuses on firms that belong to one of the most important high-tech clusters in Spain.  The research objectives are: (1) Analysis of the effect that the professional and personal characteristics of researchers and managers in firms devoted to technological innovation have on the social capital they posses; (2) effects of researchers’ social capital on three aspects of the innovation process (innovative creativity, problem solving tat requires tacit knowledge, and assessment of business viability of possible innovations); (3) analysis of the effects that the geographic location of the people that generate researchers’ social capital has both on their innovative creativity and problem solving during the innovation process; (4) analysis of the effects that the characteristics of firms and the industry have on the innovative capability of social capital; (5) analysis of the effect that the social capital that emerges from the relationships that firm managers hold with foreign professionals has on the event that their firm has or has not internationalized its innovation, commercialization, production and financial activities; and (6) analysis of the co-evolving nature of the relationship between social capital and the internationalization of firm activities.