This study uses the Diffusion of Innovations Theory to examine the role of mass media–generated interpersonal communication in the adoption of antitobacco norms among opinion leaders in California. Data were collected from 503 key community opinion leaders within 18 California counties in 1997 as part of the Independent Evaluation of the California Tobacco Control Program. Results provide support for the proposition that tobacco control policies and behaviors of opinion leaders can be categorized according to stages in the innovation decision process. As hypothesized, the level of mass media–generated interpersonal communication was dependent upon an individual's stage of adoption such that the frequency of ad discussion increased with advancing stages on the continuum. Regression analyses also confirmed a strong positive associative trend between ad discussion and stage of adoption. Further analysis provided evidence that the impact of campaign exposure on adoption of antitobacco norms was mediated through discussion of the ads, highlighting the importance of social diffusion processes. This study provides evidence regarding the importance of using a stage-based framework to understand the role of communication channels at distinct stages of innovation adoption and among various community opinion leaders.