We have previously identified tumor susceptibility gene101 (TSG101), overexpressed in vincristine-resistant human gastric adenocarcinoma cell line SGC7901/VCR using a modified subtractive hybridization method and Western blot. In the present study, we constructed two siRNA eukaryotic expression vectors of TSG101 and transfected them into SGC7901/VCR cells to examine whether the down-regulation of TSG101 increased cell sensitivity towards chemotherapeutic drugs. After transfection, the expression of TSG101 was dramatically decreased in TSG101 siRNA transfectants compared with that in parental cells and empty vector control cells. The down-regulation of TSG101 could significantly enhance the sensitivity of SGC7901/VCR cells to vincristine and adriamycin. The capacity of cells to efflux adriamycin markedly decreased in TSG101 siRNA transfectants. These observations suggested that the siRNA constructs of TSG101 we made could effectively down-regulate the expression of TSG101 and reverse the resistant phenotype of gastric cancer cells. The preliminary study suggested that TSG101 might play an important role in multidrug resistance of gastric carcinoma.