Approximately 600 elementary school children (Grades 1-6) completed a loneliness rating scale and several fitness tests. Children who scored within low, average, and high ranges on the loneliness scale were compared to determine whether there were differences in levels of reported performance on fitness tests. ANCOVA tests revealed that lonely children were less physically fit and physically active than were those who were not lonely. Grade-specific analyses revealed that the relationship between levels of loneliness and physical fitness/physical activity appears to be most profound at the third- and fourth-grade levels. The results from this study suggest that lonely children may lack the social and/or physical skills necessary to effectively interact and function in group settings (physical activity is often a social activity for children). This could potentially perpetuate a cycle of poor social interaction, rejection or withdrawal, reduced physical activity, and reduced physical fitness.