AIM:To investigate the cytotoxic activity of extracts oftrichosanthes root tubers (EOT) on HepA-H cells and HeLacells compared with trichosanthin (TCS),and to explorethe possible mechanism of growth inhibitory effect of EO-ron HeLa cells.METHODS:Tumor cells were cultured in vitro,and thenmicroculture tetrzoalium assay (MTT) was used toinvestigate drugs’ cytotoxic activity.Scanning electronmicroscopy (SEM) and transmission electron microscopy(TEM) were used to observe ultrastructural changes ofcells,and electrophoresis was performed to detect changesof biochemical characteristics of intercellular DNA.RESULTS:TCS and EOT had no obvious effects on HepA-H cells (P>0.05),but had remarkable effects on HeLa cellsin a time and dose dependent manner (r>0.864,P<0.05or P<0.01).The inhibitory rate of EOT was much higherthan that of TCS (P<0.01).Median inhibitory rates (IC50)of TCS and EOT on HeLa cells were 610.9 mg/L and115.6 mg/L for 36 h,and 130.7 mg/L and 33.4 mg/L for 48 hrespectively.Marked morphologic changes were observedincluding microvillus disappearance or reduction,cellmembrane bledding,cell shrinkage,condensation ofchromosomes and apoptotic bodies with completemembranes.Meanwhile,apoptosis of HeLa cells wasconfirmed by DNA ladder formation on gel electrophoresis.CONCLUSION:TCS and EOT have no obvious effects onHepA-H cells,but have significant inhibitory effects on HeLacells,indicating that EOT is superior to TCS in anti-tumoractivity. AIM: To investigate the cytotoxic activity of extracts of trichosanthes root tubers (EOT) on HepA-H cells and HeLacells compared with trichosanthin (TCS), and to explore the possible mechanism of growth inhibitory effect of EO-ron HeLa cells. METHODS: Tumor cells were cultured in vitro, and then culture of tetrzoalium assay (MTT) was used to investigate the drugs’ cytotoxic activity. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe ultrastructural changes of cells, and electrophoresis was performed to detect changes of biochemical characteristics of intercellular DNA.RESULTS: TCS and EOT had no obvious effects on HepA-H cells (P> 0.05), but had remarkable effects on HeLa cells in a time and dependent dependent manner (r> 0.864, P <0.05or P <0.01). inhibitory rate of EOT was much higherthan that of TCS (P <0.01) .Michen inhibitory rates (IC50) of TCS and EOT on HeLa cells were 610.9 mg / L and 115.6 mg / L for 36 h, and 130.7 mg / L and 33.4 mg / L for 48 hrespectively.Marked morphologic changes were observedincluding microvillus disappearance or reduction, cellmembrane bledding, cell shrinkage, condensation ofchromosomes and apoptotic bodies with completembranes. Meanwhile, apoptosis of HeLa cells wasconfirmed by DNA ladder formation on gel electrophoresis. CONCLUSION: TCS and EOT have no obvious effects onHepA-H cells, but have significant inhibitory effects on HeLacells, indicating that EOT is superior to TCS in anti-tumoractivity.