In a European multicenter trial the weekly rates of increase in hematocrit and reticulocyte values were investigated in hemodialyzed patients with transfusion-dependent anemia treated with recombinant human erythropoietin (rHuEPO). Within a few months of therapy, the number of transfusion-dependent patients decreased to less than 5% of the group. Patients with aluminum overload indicated by elevated basal serum levels or elevated levels after a desferrioxamine challenge showed a significantly reduced response to rHuEPO. whereas in patients with elevated levels of parathyroid hormone a normal response to rHuEPO was found.