The rotavirus nonstructural glycoprotein NSP4 functions as an enterotoxin and plays an important role in viral pathogenesis. The NSP4 gene of bovine rotavirus isolated in Korea was expressed in a baculovirus-insect cell system. Sf9 cells infected with recombinant baculovirus, inserted with NSP4 gene, produced specific cytopathic effects and the expressed NSP4 was detected by immunofluorescence staining using NSP4-specific MAb. The expressed NSP4 migrated at 20, 26, 28 kDa on SDS-PAGE and reacted with NSP4-specific MAb by Western blotting. The glycosylation of NSP4 was inhibited in culture with tunicamycin, a specific inhibitor of N-linked glycosylation, and only the non-glycosylated 20 kDa NSP4 was expressed while the glycosylated form of 26 and 28 kDa was not expressed.