Increased performance after blood transfusion was first demonstrated 40 years ago, but the technique did not create attention until the early 1970s when it was dubbed 'blood doping' by the media. The procedure can increase both maximal oxygen uptake (VO2max) and performance in endurance sports. It was forbidden by the International Olympic Committee (IOC) after the 1984 Olympics, despite the fact that no methods had been devised for unequivocal detection. There are 2 types of blood transfusions: either from a matching donor (heterologous transfusion) or reinfusion of the subject's own blood (autologous transfusion). While the subject's haemoglobin normalise, blood can be stored in commercially available blood bags for 4 to 5 weeks in a 'blood bank' (+4 degrees C), or as frozen erythrocytes with a storage time up to several years. A blood doping procedure, independent of transfusion type, induces some pronounced physiological changes. A desired effect of blood doping is the increased total red blood cell mass leading to increments in haemoglobin, which after successfully induced blood doping is in the magnitude of at least 10%. In addition, storing of blood leads to a constant decline in RBC count due to the limited life span of the RBC (haemolysis). Thereby, serum iron and bilirubin levels will increase and reach maximal levels within the first day. Haemolysis is more accentuated after storing of blood in a blood bank than in the frozen state. The regulation of RBC formation is mediated through a negative feed-back mechanism via the glucoprotein hormone erythropoietin.(ABSTRACT TRUNCATED AT 250 WORDS)