After a brief discussion of the use of the concept of social capital in political sociology, the article focuses on the social capital of voluntary associations and the relationship between social involvement, trust and political engagement. To what extent is membership in such networks of voluntary associations linked with trust, civicness and commitment to democracy? The traditional "social capital" model (attributed to Robert Putnam) is based on the idea that positive orientations towards political officeholders and institutions and commitment in politics and community affairs are reflections of more general social orientations, which are directly created by associations. In other words, patterns of social interaction affect not only citizens' trust in each other but their trust in politicians and promote political engagement. This hypothesis is tested on the basis of data collected through questionnaire administered to 132 associations and 40 activists based in Florence. The findings allow one to argue that such social and political trust is not always necessary in order to obtain a transition from social to political involvement. Perhaps it is more appropriate, when conceptualizing social capital, to separate its structural (networks) and cultural (social norms and values, and particularly trust) components.