Poor nutrition and physical inactivity are the second leading causes of preventable morbidity and mortality in the United States. Mass media campaigns have tremendous promise for reaching large segments of the population to influence these behaviors. There is still insufficient evidence in the literature, however, to recommend mass marketing campaigns for physical activity and nutrition. Successful mass media campaigns should have a formative research base that includes conducting preproduction research with the target audience, using theory as a conceptual foundation of the campaign, segmenting the audience into meaningful subgroups, and using a message approach that is targeted to and likely will be effective with the audience segment. In this study, these formative research steps were addressed to develop a mass media campaign based on the Theory of Planned Behavior to increase physical activity and fruit and vegetable consumption in 35-55-year-old adults in the state of Hawaii. For the walking campaign, our results identified time, a control belief, as the major barrier. For fruits and vegetable, the data suggested social norm (if others around me ate them) and control (if they were available). These data then were used to develop a mass media campaign based on these principals.