OBJECTIVE This study was conducted to explore the effect of Rg3 on inhibition of proliferation and induction of apoptosis in bladder cancer cells.METHODS The EJ bladder cancer cell line was treated with Rg3 at various concentrations. Cell proliferation was measured by the MTT assay. Morphological changes in the cells were observed by fluorescent staining using Hoechst 33258. The cell cycle and apoptotic rate were analyzed by flow cytometry (FCM) and the expression of caspase-3 in cells was detected by immunocytochemistry. DNA ladder analysis was conducted by agarose gel electrophoresis.RESULTS Rg3 inhibited proliferation of EJ cells in a concentration-dependent manner, resulting in an IC50 for Rg3 at 48 h of 125.5 μg/ml. When treated with 150 μg/ml of Rg3 for 24 h and 48 h, the cells showed apoptotic morphological characteristics including condensed chromatin, nuclear fragmentation, apoptotic bodies and bright fluorescent granules as well as a higher caspase-3 expression. The FCM assay indicated that Rg3 altered the cell cycle and induced apoptosis of the EJ cells, when treated for 24 h and 48 h with 75 μg/ml of Rg3 as well as for 48 h with 150 μg/ml. The percentages of cells in the S phase and the G2/M transition were increased, whereas the percentages of cells in the G0-G1 transition were decreased. The apoptotic rates were increased from (1.05±0.17)% in the control group cells to (8.41 ±0.98)%, (18.57±2.20)% and (33.98±1.64)% respectively. Significant changes in the DNA ladders, showed that the effects of Rg3 were displayed in a dose and time dependent manner.CONCLUSION The results suggest that Ginsenoside Rg3 exerts an inhibitory effect on proliferation of EJ cells by inducing apoptosis.