Using the patch-clamp technique, we studied the differences in whole-cell potassium conductance (gκ⁺) in T lymphocytes (TL) from three groups of patients suffering from renal failure: not dialyzed patients, dialyzed patients, and dialyzed patients treated with human recombinant erythropoietin (rHu-EPO). The difference in gκ⁺ values in the group of not dialyzed patients in comparison with controls was not significant (p > 0.05). In the group of dialyzed patients, after roughly 6 years of the hemodialysis therapy, the gκ⁺ value was significantly higher than in controls. In dialyzed patients treated with rHuEPO, gκ⁺ value was significantly lower in comparison with control. Moreover, in dialyzed patients treated with rHuEPO, the time duration of dialysis therapy did not significantly affect the TL whole-cell conductance. We conclude that the gκ⁺ is changed in TL in renal failure patients and that the time duration of hemodialysis therapy as well as the use of rHuEPO affect the gκ+ value. Possible mechanisms underlying the observed changes in gκ⁺ values, as well as medical implications of obtained results are discussed.