Physical activity is often recommended as a strategy for managing stress. Although associations among physical activity, stress, and hassles have been documented among adults and children, they have not been studied extensively in college populations. This cross-sectional study employed an ethnically diverse sample of 814 male and female students from three types of colleges in southern California to examine the relationship between physical activity and two indices of stress. Anonymous paper-and-pencil questionnaires were used to assess a number of psychosocial and behavioral constructs, including perceived stress, hassles, and leisure time physical activity. Significant gender, ethnic and college differences were found in levels of physical activity, perceived stress, and hassles. Hierarchical linear models showed a significant negative relationship between physical activity and hassles. Considering the deleterious effects of stress and sedentary behavior on health, these results have implications for lifetime physical and mental health. Thus, health promotion programs for college students may benefit from incorporation of physical activity strategies to reduce stress. Copyright © 2006 John Wiley & Sons, Ltd.