Human granulocyte colony-stimulating factor (hG-CSF) is one of the hematopoietic growth factors which plays an important role in stimulating proliferation, differentiation, and functional activation of blood cells. In addition to its effect on hematopoiesis, G-CSF also enhances neutrophil functions against bacteria, fungi, and tumor cells mediated by antibody-dependent cell-mediated cytotoxicity. Recombinant hG-CSF was expressed in E. coli and purified by FPLC gel-filtration chromatography, after refolding of the isolated inclusion bodies in a renaturation buffer.