Reinfusion of whole blood or packed red blood cells (RBCs) increasing the haemoglobin concentration ([Hb]) above the individual's normal values increases VO2max and enhances physical performance. During submaximal exercise heart rate and blood lactate concentration ([Hla]) are reduced, while arterial blood pressure remains unchanged despite increased haematocrit (Hct). There is no method available for detecting this type of blood 'doping'. Seven weeks of injection with recombinant human erythropoietin (rhEPO) (20-40 IU per kg body weight) increased [Hb] and Hct, maximal oxygen uptake (VO2max) and physical performance were increased. The change in VO2max per gram change in [Hb] is the same after reinfusion of blood and after rhEPO injections. During submaximal exercise arterial blood pressure is increased, which despite a reduced heart rate, puts greater stress on the circulation even in trained athletes. An electrophoretic method is available to detect the use of rhEPO but it is costly and slow and therefore it can not be used in sport. Indirect markers of increased erythopoiesis may be used. However, further research in this field is necessary.