In previous studies we reported that the levels of RBC, hemoglobulin (HGB) and hematocrit (HCT) in SAM P6 were increased significantly from 7 day after oral administration of the pilose antler extract, 5 g/kg/day, and were lasted during the study. Thus, this study was performed to elucidate mechanism of erythropoietic action by the extract administration. SAM R1 and SAM P6 were chosen as experimental animals. At age of 12 weeks, pilose antler extract were given 0.3 and 5 g/kg/day (p.o.) each for 0, 7 and 14 days in both animals. Complete blood cells such as RBC, HGB, and HCT were counted. And plasma concentration of erythropoietin (EPO) which is the major regulator of erythropoiesis was measured using $^{125}I-antierythropoietin$ IgG. Total iron concentration in plasma was also analyzed. The levels of RBC and HCT were increased significantly after administration at both doses of 0.3 and 5 g/kg/day in SAM P6, however, these were increased only at dose of 5 g/kg/day in SAM R1. The plasma EPO concentration was increased significantly after administration in SAM P6. The plasma concentrations of total iron were significantly decreased after administration of the extract in SAM P6. These results suggest that the changes in erythropoietic effects after the administration of pilose antler extract may be mediated, at least in part, through the change in the plasma EPO.