Mass media campaigns are one of the interventions used in health promotion, to stimulate population-level changes in behavior. A review of the literature found only three studies concerned with the effectiveness of national health promotion campaigns that used the mass media to promote physical activity. These showed that campaigns could help to change levels of knowledge and attitudes towards physical activity, but had limited short-term impact on physical activity participation. Reviews of the role of mass media in other health topics, also showed limited evidence of short-term behaviour change. The important broader role of campaigns is influencing the climate of public opinion in favour of health promoting public policies and providing an overall framework or umbrella under which a broader range of health promotion initiatives can take place. In particular, they appear to be useful to professionals working at a community level, as they provide the backdrop for more detailed community-level or interpersonal interventions.