Healthy People 2010 places physical activity in the top ten leading indicators of health of Americans. Yet 54.6 percent of U.S. adults report levels of physical activity that fall below the following two guidelines: moderate intensity activity 30 minutes or more per day, 5 or more days per week OR vigorous intensity activity 20 minutes or more per day, 3 or more days per week. Further, 2001 Youth Risk Behavior Survey data indicate that 64.6 percent of high school students meet the Healthy People 2010 goal for vigorous activity (3 or more days per week for 20 or more minutes per occasion), and 25.5 percent of high school students meet the Healthy People 2010 goal for moderate intensity activity (at least 30 minutes on 5 or more of the previous 7 days). Clearly, there is a need to understand how to sustainably increase and maintain physical activity behaviors in children, adolescents, and adults. The first specific aim of this review was to examine the evidence that physical activity interventions, alone or combined with diet modification or smoking cessation, are effective in helping individuals sustainably increase their aerobic physical activity or maintain adequate aerobic physical activity. Further, within this first portion of the review, there were four sub-aims: 1. Is the effectiveness of theoretically based interventions different? 2. Do hypothesized moderators affect the results of these interventions? 3. Do these interventions affect theoretically hypothesized mediators? 4. In these interventions, is there a relationship between changes in theoretically hypothesized mediators and changes in physical activity? In addition to the importance of physical activity in general populations, physical activity may play a special role in the experience of cancer survivors from the point of diagnosis through the balance of life. Understanding the impact of cancer and its treatment on individuals living years beyond a cancer diagnosis is increasingly important, especially as the population of long-term cancer survivors continues to grow. For example, it is estimated that there are approximately 9.5 million cancer survivors alive in the United States today. As children and adults with a history of cancer are living longer, the challenges that face survivors will gain increasing attention. Current cancer treatments, although increasingly efficacious for preventing death, are toxic in numerous ways and produce negative long-term physiological and or psychological effects. Because physical activity has been shown to improve well-being in healthy people, it has been proposed as a possible intervention to combat the early and late effects of treatment in cancer patients. The American Cancer Society now recommends that cancer survivors perform regular physical activity toward the goal of maintaining a healthy body weight, reducing risk of recurrence, and reducing risk for other common chronic diseases. Therefore, the second specific aim was to examine whether physical activity is efficacious for improving psychosocial or physiologic outcomes among cancer survivors.