The pharmacokinetics of CJ-50001 (recombinant human granulocyte-colony stimulating factor, developed by R&D center of Cheil Jedang Corp.) were investigated in rats and dogs. The serum concentrations of CJ-50001 were measured by a sandwich enzyme immunoassay. After single intravenous (iv) administration of Cf-50001 to rats at a dose of 5 $mu$g/kg, the mean terminal half-life and area under the concentration-time curve (AUC) were 0.96 h and 124.497g . h/ml, respectively. After single subcutaneous (sc) administration at the same dose, maximum serum concentration was observed at about 2 hours after administration, and the mean terminal half-life, AUC and the bioavailability were 1.11 h,63.58$mu$g . h/ml and 51.07%, respectively. In repeated dosing studies, CJ-50001 was administered iv and sc to rats at a daily dose of 5$mu$g/kg for 7 days. The pharmacokinetic parameters, such as mean AUC and terminal half-life, were no significantly different from those of single administration. Following single iv and sc administration of CJ-50001 to dogs at a dose of 5 $mu$g/kg, mean AUCs were much higher than those of rats, due to the decreased clearence (CL). After sc administration to dogs, maximum serum concentration was observed at 2~4 hours after administration and the bioavailability was 54.60%.