The triad of insulin, diet and exercise has been the basis for treatment of diabetes for several decades. However, the choice of sporting activities for young diabetics requires an understanding of: (a) the energy metabolism and the adaptation to physical activity in the healthy; (b) the metabolic adaptation during physical activity in the diabetic child; and (c) the practical recommendations concerning diet and insulin that have to be learned by the children themselves. The healthy child utilises immediately available substrates, such as ATP and creatine phosphate in much the same fashion as the adult. However, the capacity for anaerobic degradation of glycogen and glucose seems limited in the muscles of children relative to that of adults. Consequently, the adaptation to resistance exercise should be undertaken with prudence in children and adolescents. In diabetic children, an adequate insulin therapy is required to allow the full benefit of muscular activity on glucose assimilation and to reach the same level of physical performance as the non-diabetic. In the case of insufficient metabolic control, exercise can provoke severe hypoglycaemic episodes, even after muscle activity has ceased, or increase glucose levels and lead to ketoacidosis. Regular physical training induces a reduction in postexercise proteinuria measured in diabetic adolescents but its role in metabolic control remains controversial. If a diabetic child or adolescent follows individual recommendations concerning diet and insulin, he or she can perform physical activity much the same as a young non-diabetic. These recommendations include: (a) self-measurement of blood glucose concentration before and after exercise; (b) ingestion of carbohydrates before, during, and after exercise; (c) reduction of the insulin dose during and immediately after exercise; and (d) not choosing an injection site involved with muscular work. The only prohibited sports are those which constitute a danger to the diabetic child by provoking an eventual hypoglycaemia. The best sports are those that require progressive physical effort and that are spread out over several hours.