Baculoviruses encode fibroblast growth factor (vfgf) homologs whose function during virus infection is unknown. We constructed a recombinant bacmid of Autographa californica M nucleopolyhedrovirus (AcMNPV) lacking a functional vfgf and characterized it in two insect cell lines. The kinetics of budded virus production were similar in the parental and vfgf-deficient viruses in both cell lines at both high and low multiplicities of infection. In addition, no obvious differences were observed between the mutant and parental viruses in protein or DNA synthesis. Finally, coinfection of vfgf-containing and -deficient viruses and passage for several generations did not reveal a consistent growth advantage for either virus.