This study centers on the effect that participating in a voluntary association has on its members' general level of trust, proposing that not only a direct effect exists, but that the relationship is moderated by three specific characteristics of an association: its goals, the diversity of its composition, and the outside contacts that the association provides its members. Thus, associations proposed to create conditions fostering the spillover of personalized trust to others in society were those with the following characteristics: a) engage in activities that go beyond the attainment of its members' self-interested goals, seeking public goods beneficial to society as a whole; b) congregate dissimilar people in terms of demographic characteristics age, education, sex, regional provenance and social class; and c) foster frequent interaction with outsiders who are not similar to the members of the association.