Doping consists in the use of artificial means or substances with the unique aim of improving performance despite adverse effects on health. Amphetamines stimulate the central nervous system by increasing motivation and vigilance. Often consumed in association with analgesics, they increase the fatigue threshold during prolonged or repeated exercise. Addiction and dependency to these substances are extremely rapid. Side-effects include insomnia, exhaustion, violence and can lead to serious heart diseases. By enhancing capacity for intensive training, anabolic steroids improve strength, alertness and speed. This action is often further strengthened by the use of growth hormones DHEA and IGF-1. Extremely high dosage is used and is in no way comparable with natural secretions or those necessary to re-balance an exhausted glandular system. During prolonged endurance exercise, doping aims at improving the circulation of oxygen in the blood and thus its availability to the muscles. Firstly, the blood haemoglobin concentration was increased by blood transfusions. At present the production of red blood cells is stimulated by repeated injections of exogenous erythropoietin. The extreme viscosity of the blood leads to a risk of vascular thromboses and high blood pressure and accentuates greatly and sometimes even fatally the possibility of brachycardia which is common with sportsmen.