Abstract: Objective To evaluate the chemopreventive effect of celecoxib,a specific cyclooxegenease-2(COX-2) inhibitor,on chemically induced breast cancer of rats and its effect on COX-2 expression.Methods 7,12-dimethylbenz anthracene(DMBA) was administered intragastrically in SD female rats to establish breast cancer models,which were divided subsequently into control group,tamoxifen group and celecoxib group to receive different treatments accordingly.The occurrence rate of breast cancer was observed and the effect of celecoxib on COX-2 and vascular endothelial growth factor(VEGF) expressions assayed by immunohistochemical SP method.Results The incidence of breast cancer in tamoxifen group(48.15%) and celecoxib group(50.00%) were both significantly lower than that in the control group(85.71%;P=0.003 and P=0.004,respectively).The positivity rate of COX-2 expression in celecoxib group(28.57%) was significantly lower than those of tamoxifen group(48.15%) and control group(83.33%;P=0.001 and P=0.035,respectively).The positivity rate of VEGF expression in celecoxib group(42.86%) was significantly lower than that of control group(79.17%,P=0.023),but comparable with that in tamoxifen group(46.15%,P=0.863).Conclusion Celecoxib can significantly suppress DMBA-induced breast cancer in female rats possibly through down-regulation of COX-2 and VEGF expressions.