There is currently a large breast cancer chemoprevention trial in Italy. The trial is based on the use of the antioestrogen tamoxifen, which is one of the most successful and most studied anticancer drugs. There is a strong evidence that this drug can prevent the growing of controlateral cancer in women previously operated for breast cancer. The chemoprevention trial using tamoxifen includes healthy women, aged 35 to 70 and hysterectomised. The participants are taking either 20 mg/day of tamoxifen or placebo for 5 years, in double blind; then they are followed-up clinically and instrumentally every 6 months for the further 5 years. The main end-point of the study is to verify the reduction of incidence and mortality from breast cancer. It was decided to recruit only hysterectomised women on the consideration that, according to some studies, tamoxifen could give an additional risk of endometrial cancer: the Italian study was especially designed with the intention of avoiding this unjustified risk.