The authors review the role of physical exercise in reducing childhood and adolescent posttraumatic stress disorder, anxiety, and depression. A good deal of the existing research on the influence of exercise in reducing negative emotional states and enhancing perceptions of self-efficacy has been conducted with adult samples. Comparatively few empirical studies that target children and adolescents have been done; however, those that have been conducted support the efficacy of exercise, particularly aerobic exercise, in reducing negative emotional states. The authors review a number of explanations for these beneficial effects. Although no explanatory position has received universal support, the psychological benefits of exercise appear to be compelling. The use of exercise programs in schools can be beneficial to children's physical health and valuable to emotional health.