Abstract: To investigate the effects of all-trans retinoic acid （ATRA） on the growth of gastric cancer cells in nude mouse xenografts,three gastric cancer cell lines,MGc80-3,BGC-823 and SGC-7901,were treated with 10^-6 mol/L ATRA for 20d,and then inoculated subcu-taneoiLsly in the right hind legs of nude mice respectively,while the untreated ones in the left hind legs. Four weeks after the implantation,the nude mice were executed,the xenografts were removed and examined pathologically. The results showed that the incuba-tion periods and/or the double times of the xenografts of the treated group were prolonged,and their growth was inhibited significantly with inhibitory rates of 51.4% （MGc80-3） ,66.0% （BGC-823） and 88.6% （SGC-7901） respectively,These indicated that ATRA treating in vitro could inhibit the growth of the gastric cancer cells in nude mouse xenografts，and the degrees of inhibition were negatively correlated with the malig-nancy of the cancer cell lines.