Civil society organizations are often seen as repositories of social capital, and their existence is taken as evidence that the dilemma of collective action has been resolved and that there is a willingness to trust, share and cooperate. Thus, attitudes and structures are seen as two complementary elements in the social capital debate. This article suggests that attitudes and structures are not always matched. Research carried out in two Nicaraguan villages shows that there is a major contradiction between the structure of associational living and the structure of social capital at the local level. Rather than being agents of social transformation, organizations tend to institutionalize local divides in the form of social, political or economic segregation.