Novel hG-CSF polypeptide derivatives having an amino acid sequence derived fromthe amino acid sequence of the human granulocyte colony stimulating factor polypeptide by substitution of at least one amino acid by a different amino acid and/or deletion of at least one amino acid, recombinant plasmids containing a DNA fragment insert coding for any of these hG-CSF polypeptide derivatives, microorganisms carrying one of such plasmids, methods of producing the hG-CSF polypeptide derivatives using the microorganisms, a monoclonal antibody binding to the hG-CSF polypeptide derivative, and chemically modified hG-CSF or derivatives thereof are disclosed.