This a comparative evaluation of the influence of tamoxifen and toremifene on hormonal level in breast cancer patients after radical operation. 23 patients received tamoxifen, 12-toremifene. Tamoxifenum was prescribed in a dose of 10 mg daily, and toremifene given in a dose of 15 or 30 mg, toremifene-1.5 or 30 twice a day. Hormonal investigations were conducted using a radioimmunologic kit before and 3-6 months after the beginning of hormonal treatment. 3 months after the beginning of tamoxifen treatment the estrogen level, especially oestradiol, in 70% of patients increased 334 times, in half of patients testosterone, progesterone, prolactin and cortisone was reduced. At 6 months the oestradiol level appeared to be augmented 4-5 times. During toremifene treatment the increase of estrogen in blood was absent or increased in 15-2 times less than after tamoxifen treatment. Progesterone level was increased and prolactin was reduced. The dynamics of blood hormonal levels after tamoxifenum treatment shows its oncogenic danger. Toremifen in such case compares favourably with tamoxifen.