The results provide preliminary evidence to suggest that the theory of planned behavior (TPB) is useful for understanding physical activity in young people who smoke. TPB may provide a useful guiding framework to consider in the development of physical activity interventions for young people who smoke. Strategies that can enhance normative beliefs may be important when promoting physical activity in young people who smoke. It has been hypothesized that physical activity may be useful as a smoking prevention-intervention for young adults. TPB is a leading social-cognitive theoretical model of the influences on physical activity behaviors. It has demonstrated utility in predicting the physical activity behaviors of general populations of young people. However, to date no research has applied the TPB to young people who smoke. This study of 124, 16 to 19 year old regular adolescent smokers evaluated TPB in an attempt to understand physical activity behavior among young smokers. Tables, references