This study investigates whether, and to what extent, community organizations can serve as viable channels of health information. We use Putnam's (2000) findings on social capital to argue that organizations can serve two major functions in health campaigns: instrumental (e.g., providing material support) and affinity (social support). Through a secondary analysis of data from the Stanford Five-City Project, we find significant support for our predictions about who joins community organizations. Membership in community organizations explains greater variance in health outcomes than that explained by general media use, demographic indicators, and health-specific media use. Implications for health campaigns are discussed.