Iron overload increases the risk of bacterial infection in dialysis patients, partly by impairing functions of the polymorphonuclear granulocytes (PMNs). PMN defence was studied sequentially in haemodialysis patients with transfusional haemosiderosis, treated for 6 +/- 1.5 months (n = 8) to 13 +/- 1.7 months (n = 4) with recombinant human erythropoietin (rHuEpo). Over this period, signs of iron overload (increased serum ferritin and serum iron) improved, and stainable iron disappeared in PMNs. Simultaneously, phagocytosis of Yersinia enterocolitica by PMNs improved. The decrease in serum ferritin was significantly related to the improved phagocytosis. Killing of Y. enterocolitica by PMNs also improved. It is anticipated that rHuEpo therapy in iron-overloaded dialysis patients could decrease the incidence of bacterial infection by improving PMN functions in these patients.