The subject of this study was the effect of erythropoetin (Epoetin) treatment of anemic patients (n=30) with solid tumors on parameters of hemorheological profile. Both prior to and following Epoetin treatment (10,000 units subcutaneously thrice weekly) for four weeks hemorheological measurements included plasma and red blood cell (RBC) suspension viscosity; high and low shear whole blood viscosity; hematocrit (Hct), hemoglobin, RBC aggregation (RBCA) and deformation. It was found that the patients had reduced Hb up to 92.96+/-2.99 g/l, and the Hct - 28.2%. These parameters were significant increased after four weeks of Epoetin treatment: Hb by 28% (p<0.01) and Hct by 31% (p<0.01). In macrorheological part of the profile, both the high shear blood viscosity, and the low one were increased by 23 and 27% (p<0.05), respectively. These changes were mainly associated with the Hct rise. As for microrheological part of profile after Epoetin treatment, RBCA was decreased by 25% (p<0.05). While the red cell rigidity index (Tk) was lowered only slightly (by 8%). RBC incubation with Epoetin (10.0 I.E./ml) was accompanied by 10% decrease of Tk. It is important to note that before Epoetin treatment incubation with it led to decrease of RBCA by 30% (p<0.05), whereas after four week of the treatment period a 27% (p<0.05) rise of aggregation was found in majority of patients. Thus these results suggest that Epoetin is an effective, safe and convenient therapy for the management of anaemia in patients with cancer. And this drug has a moderate positive hemorheological effect on RBC and on the microrheological properties in particular. These data suggested that Epoetin has an effect on the membrane properties regulating RBC aggregation and deformation and affects by the signal transduction system, including Ca2+-dependant signaling pathway and tyrosine kinase and phosphotase activity change.