A partial cDNA of human Stem Cell Factor (SCF) was isolated and transferred into the genome of Bombyx Mori Nuclear Polyhedrosis Virus adjacent to the polyhedrin promoter. The soluble form of the SCF protein was expressed in Bombyx Mori cells and silkworm larvae and was secreted into the medium in an active state. The recombinant SCF was similar to natural SCF with respect to its interaction with monoclonal antibody and its synergistic biological activity in conjunction with colony-stimulating factor.