The Physical Activity Counselling (PAC) randomized controlled trial had as overall goal the establishment of a collaborative interdisciplinary primary care team to encourage physical activity. The main intervention was to integrate a physical activity counsellor to the primary care team so that the most appropriate care was given by the most appropriate provider. Much research has shown and many experts agree that patients need significant help to make and especially maintain physical activity behavior changes. Maintenance of these changes is essential for optimal health benefits. It was predicted that patients receiving both brief (2-4 minute) physical activity counselling from their family physician and intensive (3 month) physical activity counselling from an integrated physical activity counsellor (intensive counselling group) would report greater improvements in task motivation and task self-efficacy to engage in physical activity at the end of the intervention than those receiving only brief counselling (brief counselling group). The same was expected for both self-reported and objective physical activity. This RCT involved testing a theory-based counselling intervention, determining why the intervention was effective or ineffective by measuring key psychological mediating variables, using an objective measure to track changes in physical activity, and assessing physical and metabolic outcomes. This project represents an innovative theoretically based multi-level multi-intervention approach to promoting physical activity in primary care and is of great public health importance.