The pharmacokinetics of recombinant human granulocyte colony stimulating factor (rhG-CSF) following intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) administration of HM1041l-lyo and HM10411-liq (lyophilized and liquid formulations of rhG-CSF, recently under development by Hanmi Pharmaceutical Company) were studied in rats, and compared with that of Filgrastim (conventional formulation of rhG-CSF on market). The plasma concentration of rhG-CSF was quantified using a specific ELISA. The pharmacokinetic parameters of rhG-CSF, after i.v., i.m. and s.c. administration of Filgrastim, HM1041l-lyo and HM1041l-liq to rats at a rhG-CSF dose of $10;{mu}g/kg$, were almost identical among the three formulations. No dose-dependency was observed in the pharmacokinetic parameters of rhG-CSF following i.v. administration in the dose range of $5{sim}100;{mu}g/kg$. rhG-CSF, after i.v. administration of the three preparations at a dose of $10;{mu}g/kg$ to rats, was detected at low levels in all of the body tissues with highest tissue/plasma ratio of $0.46{sim}0.51$ for the kidney at 30 min after the administration. The pharmacokinetics of rhG-CSF, after i.v. administration to mice at a dose of $10;{mu}g/kg$, were comparable among the three formulations. In conclusion, HM10411-lyo and HM10411-liq exhibited similar pharmacokinetics for rhG-CSF with Filgrastim regandless of animal species. Considering the fact that HM10411 series, contrary to Filgrastim, are proteins lacking a methionine residue, the methionine moiety in rhG-CSF molecule does not appear to influence the pharmacokinetics of the protein significantly.