Evidence-based public health takes many of the principles of evidence-based medicine and applies them to public health. This is a relatively young discipline however and is not universally applied to public health issues--especially such multidisciplinary topics as physical activity. This paper sets out to provide guidance on this issue by characterising four 'key tasks' that form the basis of a systematic evidence-based approach to promoting physical activity. These tasks are based in part on the physical activity promotion model (Brownson et al.,1999). These are illustrated with examples from work in three contrasting European countries: Finland, England and Switzerland. 'Task one' is concerned with using the evidence for the health benefits of physical activity to 'make the case' and increase action by policy makers. Here, all three countries took a similar approach, conducting academic reviews to draw together the existing evidence of the health benefits of physical activity. 'Task two' is concerned with conducting surveillance to collect evidence on the prevalence of physical activity. Here, Finland and Switzerland were careful to collect trend data and use them for advocacy, while in England continuous changes to questionnaires and survey methodologies have led to poor trend data. 'Task three' is to review evidence on 'what works' in increasing physical activity to influence practice. England appears to be taking a more systematic approach to this task, with a comprehensive approach to reviewing evidence on what works and disseminating this to influence good practice, while the other countries rely mainly on individual evaluation studies. 'Task four' is the evaluation of practice and it is clear that in all three countries this remains a significant challenge--one requiring additional training and dedicated funding. As a result much of current "good practice" is based upon experience (usually unevaluated) and not evidence. This brief analysis shows that there are some common tasks that need to be undertaken as a central part of an evidence-based public health approach. However, cultural and political factors in each country studied have influenced the manner in which these tasks were undertaken, and the importance attached to each component.