The naming of physical inactivity as a major risk factor for cardiovascular disease' combined with the high prevalence of physical inactivity in industrialised nations is spurring development of research efforts that examine how to increase physical activity. between 1966 and 1996. Combinations of the following key words were used to develop a comprehensive list. These included exercise, physical activity, primary prevention, intervention, adherence, compliance, leisure activity, evaluation, effectiveness, behaviour, psychology, public health, health promotion, and epidemiology. The search was limited to studies in adults. The rationale for limiting the review to adults is based on evidence that determinants of physical activity differ between children and adults2 and on my belief that adoption of physical activity by children should be a topic for a separate review.Other studies were identified from these references and from existing reviews on determinants of exercise or physical activity. Studies were classified as being either observational studies of populations, examining the question of adoption of physical activity or exercise, or