The transfusion of red blood cells is still associated with possible adverse effects and a residual risk of transmission of viral and nonviral diseases. In addition, there is an increasing shortage of blood supply worldwide. These two facts together with the success experienced in the treatment of various types of anemia with recombinant human EPO, have recently led to an increasing interest in the anemia of critically ill patients. As in the anemia of chronic diseases there are several reasons that contribute to the development of anemia in patients on intensive care units: preexisting anemia, blood loss, reduced red cell life span, impaired iron availbility and a direct inhibition of erythropoiesis by inflammatory cytokines. The implications of anemia for the progression and prognosis of critical illness are still unclear and the optimal treatment, including optimal "transfusion triggers" remains controversial. Recombinant human EPO has been proven to be effective in ameliorating the anemia of critical illness in several pilot studies and is currently being tested in larger trials.