Objective To investigate expression of 14-3-3 sigma gene in patients with breast cancer and its clinical significance.Methods Expression of 14-3-3 sigma gene was semi-quantitated by using RT-PCR and western-blot in 40 specimens of breast cancer and 18 specimens benign breast disease tissue.Results Of 40 cases of breast cancer 35(87.5%)were negative for 14-3-3 sigma gene in RT-PCR,32(80%)were negative in Western-blot,and 31(77.5%)were negative in both RT-PCR and western-blot.Besides,the expression in 2 cases was down-regulation in both the 2 method.In 18 specimens with benign breast disease tissue the expression of 14-3-3 sigma gene was detectable,which was demonstrated by RT-PCR or western-blot.Conclusion Inactivation and down-regulation of 14-3-3 sigma gene is a frequent event in breast cancer,and it may contribute to diagnosis of breast cancer.