The purpose of this review was to examine seasonal variation in physical activity among children and adolescents. Searches were conducted of electronic databases for studies on seasonal differences in physical activity levels. A total of 35 studies, including children and adolescents between the ages of 2-19 years, were reviewed. Overall, 83% (29/35) of the studies found seasonal variation in physical activity among children and/or adolescents. The results were consistent regardless of the region, physical activity measure, or the study design but the findings were inconsistent across age categories.