Effects of methanol extract of Terminalia chebula on antibacterial activity and the generation of superoxide radical in Bacillus subtilis, as well as on syncytium formation and cytopathic activity in virus-infected baby hamster kidney cells were examined. The extract effectively inhibited syncytium formation in a concentration-dependent manner, and infectious virus production was markedly reduced. However, glycoprotein synthesis was not affected. These results collectively indicate that methanol extract of T. chebula potentially inhibit glycosylation by acting as a suppressor of intracellular glycosylation trafficking.