The monopoly of insect cells to host baculovirus Autographa californica multiple nuclear polyhedrosis virus (AcMNPV) as a eukaryotic gene expression system has been shattered with the growing evidence that it also infects mammalian cells in culture. Although AcMNPV fails to replicate in vertebrate cells, it does express alien genes with levels of expression that are dependent on the strength of the promoter used to drive transcription of the foreign gene. It also has been reported that the recombinant AcMNPV enters human hepatic cells in culture preferentially and specifically in comparison with the other mammalian cells of different origin and sources. This has resulted in the use of AcMNPV as a potent mammalian cell delivery system as a xenovector for gene therapy, more precisely liver-specific gene delivery in vitro and in vivo.