Recent advances of the research on synergistic effect of a mixed baculovirus infection demonstrated the presence of viral molecules enhancing the early event of infection. The enhancins from the Trichoplusia ni was identified to have such a function, i.e., disrupting the structural integrity of peritrophic membrane of midgut of T. ni larva. The enhancin gene was ligated downstream of the CaMV 355 promoter of a binary vector pBI121. With a drug resistant gene, the gene was introduced to a piece of tobacco leaf, from Nicotiana tobacum cv. Havana SR1. We screened 11 regenerated plants out of 37 by feeding tobacco powder mixed in artificial diet, to 3rd instar Pseudaletia separata larvae. The larval stage was usually delayed from 1 to 3 days in comparison of that of control larvae. The larvae did not pupate normally. The larvae showed irregular morphology of half larva and half pupae, suggesting a hormonal disturbance caused by the transgenic tobacco. The introduction of an enhancin gene into plants is an effective method of protecting them from insects due to the disruption of their normal life cycle.