The aim was to evaluate the influence of red blood cells (RBC) transfusion on the development of cytotoxic antibodies (C-Ab) in patients subjected to hemodialyses (HD) and planned for the kidney transplantation. The group of 71 HD patients, of mean age 42 years (19-65), 48 males and 23 females, planned for the kidney information was examined. Out of 71 HD patients, only 42 (59.19%) HD patients (group I) received subcutaneously recombinant human erythropoietin--rhuEPO (Eprex--epoetin-alpha or Recormon SE--epoetin-beta in dosage of 4,000 IU during every HD; i.e. one to three times a week) and they were not treated by RBC transfusion. The other 29 (40.85%) HD patients (group II) received RBC transfusion: 18 (62.07%) HD patients received < 10 units 18 of RBC, 8 (27.59%) HD patients received 10-20 units of RBC; 3 (10.35%) HD patients received > 20 units of RBC. Testing of C-Ab was done in all patients every three months by standard lymphocytotoxicity test on the panel from 20 different lymphocyte donors with definite class I phenotype of antigen HLA. C-Ab was not found in HD patients who were not treated by RBC transfusion. Out of 18 HD patients who received < 10 units of RBC only 3 (16.67%) HD patients developed C-Ab; out of 8 HD patients who received 10-20 units of RBC, in 4 (50%) patients was proved C-Ab; and C-Ab was proved in all 3 HD patients who received > 20 units of RBC. RhuEPO administration is very important for the transfusiologic treatment of HD patients; especially those who are planned for the kidney transplantation. Development of C-Ab is in direct correlation with the number of transfunded units of RBC. HD patients who received 10 or more units of RBC were at great risk to develop C-Ab.