The pharmacokinetics and biological activities of recombinant human granulocyte colony-stimulating factor (hG-CSF) produced in Escherichia coli were compared with those of hG-CSF purified from human bladder carcinoma cell line 5637 culture medium (5637-hG-CSF). Recombinant hG-CSF was biologically active in a bone marrow cell proliferation assay in vitro, with a dose-response curve similar to that of 5637-hG-CSF. The effects of 5637- and recombinant hG-CSF administered via i.v. injection to rats showed similar response patterns of neutrophil counts in peripheral blood. From these results, it is concluded that the O-linked sugar chain of hG-CSF does not contribute to the in vitro and in vivo biological activities. The pharmacokinetics of both forms of hG-CSF in rats were investigated using a sandwich enzyme-linked immunosorbent assay. After i.v. administration, the serum concentration-time curves of 5637- and recombinant hG-CSF declined biexponentially. Total body clearance and steady-state volume of distribution of 5637-hG-CSF were smaller than those for the recombinant form. After s.c. administration, a lower peak serum level, smaller AUC, and lower bioavailability of 5637-hG-CSF were observed compared to recombinant hG-CSF.