Insect baculovirus-encoded ecdysteroid UDP-glucosyltransferase (EGT) are not essential enzymes which catalyze the conjugation of ecdysteroids with UDP-glucose. In vivo, the sugar conjugation of ecdysteroids by EGT causes suppression of host molting. The deletion of egt gene actually improves the pesticidal properties of the baculovirus. Insects infected by an egt-minus virus display reduce feeding and earlier death than those infected by wild-type virus. The recent advances in the studies of the egt gene and protein, EGT-catalyzed conjugation, EGT effects on host development and suvival as well as biological role of EGT are introduced.