Exercise immunology is one of the fastest growing disciplines of the past 2 decades. Unfortunately, the number of investigations devoted to the pediatric population remains low, and our understanding of the interaction between acute and chronic exercise and the immune system in youth is relatively deficient. In general, healthy children experience smaller overall perturbations to the immune system in response to an acute bout of exercise as compared with adults, and they demonstrate a faster recovery of the immune system following exercise. There is only limited evidence to suggest that moderate to high levels of habitual physical activity are associated with a reduction in the incidence of infection and illness in youth. Special consideration should be made for the young athlete training and competing during an illness or infection. Some of the unique exercise responses of the immune system in children may have important clinical relevance, but much more work is required in this area.