Considerable advances have been made in exercise immunology over the last two decades, and it is becoming evident that many of the health benefits of regular physical activity may be directly related to activation of the immune system. The number of investigations devoted to the paediatric population, however, remains low, and our understanding of the interaction between acute and chronic exercise and the immune system in youth is, therefore, relatively deficient. The purpose of this review is to disseminate the existing knowledge in the area of paediatric exercise immunology and to discuss growth-related issues with respect to exercise and the immune system in health and disease. In general, healthy children experience smaller overall perturbations to the immune system in response to an acute bout of exercise, and demonstrate a faster recovery of the immune system following exercise. The immune effects of chronic exercise and/or exercise training in healthy children and adolescents have not been well-documented, and 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. A number of paediatric clinical conditions expressing a strong immune component are also discussed in the context of acute exercise effects and the potential benefits of enhanced physical activity. Given the linkage between childhood health and adult disease, paediatric exercise immunology represents a fruitful area for future study.