The evaluation of a campaign to increase cardiovascular health knowledge indicates that within the treatment community, education was a significant predictor of knowledge before the campaign but was not a significant predictor after the campaign. Two variables related to motivation to acquire information about cardiovascular health (age and perceived threat of heart attack) were not significant predictors of knowledge before the campaign but were significant predictors afterwards. These results suggest that the infusion of information into a social system via the mass media can close as well as open knowledge gaps and that motivation to acquire information in a specific knowledge domain is a factor controlling gap effects.