Abstract: Objective :o study the effect of allicin on human gastric cells BGC-823 and SGC-7901 and the combined effect of allicin with chemotherapeutic drugs to these cancer cells. Methods :To evaluate the inhibition rates of proliferation of cells and the ICso of 72 hours of these cells by M7,to analyze the change of cell cycle using flow cytometry, to study the change of cytotoxicity of NVB, 5-FU, MMC and PDD after combination of allicin with these chemotherapeutic drugs. Results :The cellgrowth of BGC-823 and SGC-7901 was inhibited by allicin and the 72-hour ICso of allicin was 30 ml and 20ug/ml respectively. After these cells were treated by allicin at the concentrations of 30ug/ml and 20ug/ml for 24 and 48 h respectively, the percentage of Go/G, phase of the cells was decreased and that of GZ/M phase cells was increased significantly in the allicin treated group, compared to the control group. It was shown that allicin caused arrest of gastric cancer cells in GZ/M phase. In compari-son with ICSO of NVB, 5-FU, MMC and PDD alone or combined with allicin, the 72-hour ICso value of NVB in BGC-823 cells decreased from 9ug/m1 to 2.25ug/m1, and that of 5-FU, MMC and PDD decreased from 6.25ug/m1, 12ug/m1 and 0.07ug/ml to 5.8ug/m1, 9.8ug/m1 and O.15ug/m1 (P>0.05), respectively; then the 72-hour ICSO value of NVB in SGC-7901 cells decreased from 43ug/m1 to 12.Sug/ml,0.38ug/ml and 1.0ug/mlcells BGC- 823 and SGC(P>0.05), respectively. Conclusions :Allicin has an inhibitory effect 7901. It can arrest gastric cancer cells in GCM phase and may enh on gastricance cytotoxicity of cell cycles specific chemotherapeutic drugs on the cancer cells.