Abstract: Objective To investigate the effect of pseudolaric acid B (PLAB) on cell growth of human gastric carcinoma cells in vitro. Methods The expression of PPARγ was detected by RT-PCR; the effect of PLAB on cell growth was tested by MTT; Hoechst33342/PI and DNA gel electrolysis were employed to examine on apoptosis; cell cycle was checked by flow cytometry. Results : When treated with 0.1～10 μmmol/L PLAB for 72 h, the proliferation of MGC803 cells was significantly inhibited. The proportion of MGC803 cells at G2 phase was significantly increased when treated with 10μmmol/L PLAB after 48 h, and showed an apparent G2 phase arrest. When treated with PLAB for 72 h, typical apoptotic changes were observed. The expression of PPARγ was at a low level in MGC803 cells and up-regulated when treated with 10μmmol/L PLAB for 48 h （P<0.01）. Conclusion: Activation of PPARγ induces G2 phase cell cycle arrest and cell apoptosis in vitro.