The focus of this research is to describe the production and characterization of the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) in insect cells, using Autographa californica buclear polyhedrosis virus (AcNPV) as an expression vector. All three forms of biological activity of hGM-CSF. Following N-glycanase treatment, the two glycosylated hGM-CSF proteins (15.5 and 16.5 KDa) which bound to Concanavalin A affinity column ran as a 14.5-15.5 KDa band on SDS-PAGE. Western blot analysis of expression in Sf9 cells treated with tunicamycin revealed only the presence of the 14.5 KDa species. The N-terminal amino acid sequence of the recombinant hGM-CSF was identical to that of natural hGM-CSF deduced from cDNA. These results demonstrate that baculovirus-produced hGM-CSF could be N-glycosylated in Sf9 cells, the signal peptide of recombinant hGM-CSF could be recognized and cleaved by infected insect cells and the resultant molecule secreted into the medium.