Objective To study the influence of soybean isoflavones on occurrence and development of breast cancer in MMTV-erbB-2 transgenic mice.Methods In 90 female MMTV-erbB-2 transgenic mice,60 mice received surgical castration to create a low estrogen environment,in which 30 mice were fed with soy isoflavones diet(soy isoflavones group) and 30 mice were given normal diet.The other 30 mice receiving normal diet were as controls(control group).The latency and occurrence of breast tumor were observed.Immunohistochemi...