In premenopausal women, endocrine adjuvant therapy for breast cancer primarily consists of tamoxifen alone or with ovarian suppressive strategies. Toremifene is a chlorinated derivative of tamoxifen, but with a superior risk-benefit profile. In this trial, we sought to compare the efficacy and tolerability of toremifene and tamoxifen therapy in premenopausal patients with operable,estrogen and/or progesterone receptor positive breast cancer patients.