Background : Recombinant human erythropoietin(rhEPO) is effective in correcting the anemia of chronic renal failure patients. However. the clinical application of rhEPO is limited due to its high cost. To maximize the cost effectiveness in the use of rhEPO, the dosage and frequency of rhEPO administration must be as small as possible. There is accumulating evidence that the subcutaneous administration has several advantages, but some debates exist in subcutaneous bioavailability. Method : To evaluate the subcutaneous bioavailability of rhEPO. the cross-over SC and IV pharmacokinetic studies of rhEPO have been performed in 7 chronic renal failure patients undergoing intermittent hemodialysis. Fifty units(U) of rhEPO per kilogram of body weight were administered to the subject with at least two week interval. Plasma erythropoietin levels were determined by radioimmunoassay up to 72 hours after the doses. Results : Mean plasma half-life and volume of distribution of rhEPO after IV dose were $9.8{pm}5.6({pm}S.D.)$ hours and $115.8{pm}44.8ml/kg$, respectively. Subcutaneous administration of rhEPO resulted in a slow increase of rhEPO levels which reached a maximum of 56.3{pm}47.3mU/ml at about 18hours after the dose. The subcutaneous bioavailability of rhEPO determined by $AUC_{SC(0-72hr)}/AUC_{IV(0-72hr)}$ was $30.9{pm}11.2$ percent. Conclusion : The level of plasma rhEPO was significantly long-lasting after subcutaneous administration compared with that of intravenous dose, though the subcutaneous administration showed a low bioavailability of 30.9 percent However, more clinical data are necessary before recommending the SC route as preferable.