The present invention provides methods for treating and preventing gynecomastia by administering 4-hydroxy tamoxifen to a patient. When percutaneously administered to a patient's breasts, 4-hydroxy tamoxifen concentrates locally, and exerts an anti-estrogenic effect. In patients with gynecomastia, this reduces the effective estrogen-androgen ratio in the breast tissue, thereby reducing ductal proliferation, epithelial and stromal hyperplasia, and pain. In patients at risk for developing gynecomastia, 4-hydroxy tamoxifen's anti-estrogenic effect prevents tissue proliferation and its accompanying pain.
