The OBJECTIVE of this randomized clinical trial was to evaluate the effectiveness of an innovative programme to promote physical activity (called PEPAF) implemented by family doctors into daily routine practice. Doctors randomly allocated to the PEPAF group identified sedentary people who visited them for any reason, diagnosed their stage of change and prescribed a written plan of physical activity with those patients ready to change. Those not prepared to change were briefly counseled and given printed materials to motivate them. Patients with cardiovascular disease or other problems meaning that exercise could cause adverse effects were excluded.