The argument advanced in this paper is that interaction in social networks has a strong, though often overlooked, influence on the individual propensity to participate in politics. Specifically, I argue that social interaction creates opportunities for individuals to gather information about politics that allow them to live beyond personal resource constraints, thereby supporting the political activity of many people. Using relational data from the South Bend election survey, this paper provides evidence that the effect of social interaction on participation is contingent on the amount of political discussion that occurs in social networks. Additional analysis shows the substantive and theoretical importance of such interaction by explaining how it is distinct from the effect of social group memberships and how it enhances the effect of individual education on the probability of participation. This key contribution of this paper is to show that models of political participation that do not account for informal social interaction will be theoretically underspecified. It also shows that such interactions play a crucial role in explicating the role of other factors that predict participation, such as group membership and individual resources.