5 deeply anemic (Hb less than 8 g/dl, Ht less than 25%) dialyzed patients with chronic renal failure were treated during four months with r-Epo. Blood cells morphological parameters were estimated using hematological autoanalyser Technicon H1. Satisfactory increase of the Hb levels and RBC counts were observed in 4 patients, in one the improvement was insignificant. We observed three types of response to r-Epo treatment: 1) macrocytic type, 2) hypochromic type, and 3) non-hypochromic type, without lasting macrocytosis. Our results suggest that type of erythropoiesis depends on other active biological substances (iron, folic acid, vit. B12) necessary for correcting erythropoiesis. r-Epo administration appeared to be a safe and effective method of anaemia treatment in dialyzed patients. Its administration eliminated blood transfusion for six months.