Fadrozole (CGS 16949 A, brand name: Afema) is an aromatase inhibitor developed firstly in Japan. This compound reduces estrogen levels in the body after administration, suppressing the growth of breast cancer. In animal experiments, this showed an inhibitory activity in vivo against estrogen-depended mammary tumor and the effect was potentiated by the combination of tamoxifen cytrate. In the domestic clinical trials against post-menopausal advanced-recurrent breast cancer, irrespective of the cases with ER positive or negative and even including pretreated cases, the compound showed response rate of 19.3%, the rate of long NC of 18.2%, and the total response rate of 37.5%. The prognosis of NC cases was similar to the effective (CR + PR) cases. The median survival time was 323.5 days which were better than the previous endocrine therapies. The side effects mainly consisted of nausea, vomiting, loss of appetite, abdominal pain, and fatigue, but these were all the level of grade 1. This compound-seemed to be a promising drug for the treatment of patients with post-menopausal breast cancer.