The impairment of function of human T lymphocytes, leading to an inappropriate cytokine production, is partially responsible for defective immunological response in hemodialysis patients (HD). Recent data suggest that recombinant human erythropoietin (rhEPO) may exert immunological effects. The aim of this study was to find out whether rhEPO treatment of the HD patients may have an effect on the interleukin 2 (IL-2) production by their whole blood cell cultures. The study was carried out in 10 HD patients receiving rhEPO for 6 months. Compared with the levels seen before the treatment, the concentration of IL-2 increased in the phytohemagglutinin-stimulated whole blood cell cultures of 7 of 10 patients under study. Addition of rhEPO in vitro to the whole blood cell cultures of the HD patients before implementation of erythropoietin confirmed that rhEPO is able to directly stimulate IL-2 production. Our studies show that the therapy with rhEPO affects IL-2 secretion.