In contrast to recreative sports, competition should not be allowed in children without regulations and supervision. Physical handicaps should be carefully looked for through a thorough pre-participation examination and appropriate physical activities should be defined for handicapped children. Hypoactivity, fear of accident and functional deterioration cause more damage to these children than physical training which may include competition provided the underlying disease is adequately treated. Regular physical exercise appears to provide significant physical and psychological benefits which are effective beyond the period of physical activity. Stress and aggressivity linked to competition do not seem to have harmful effects on child mental health, with an exception for elite adolescent athletes for whom more information is needed. These athletes are at risk for orthopaedic lesions by overuse as well as disturbances of cardiac and endocrine functions which may disqualify them temporarily for sport events. Treatments designed to boost performance such as anabolic steroids, amphetamines or blood transfusions should be strictly forbidden.