Anti-androgen induced gynecomastia, resulting from a treatment induced imbalance between oestrogens and androgens, is a frequently encountered side effect in the hormonal treatment of patients with prostatic cancer. One might expect to face an increase in the overall incidence of this side effect in the next-coming years as randomized trials clearly point to the evidence of the therapeutic benefit of anti-androgenic treatment for this prostatic cancer. Gynecomastia is often accompanied by mastodynia and does hamper quality of life. Surgery should be considered for established irreversible gynecomastia characterized by hyalinization and extensive fibrosis. However, radiotherapy is the treatment of choice for gynecomastia at it's early stage, or could eventually be considered as a prophylactic treatment in high risk patients. It is a safe and extremely well tolerated treatment resulting in a high degree of therapeutic success with a demonstrated effect on quality of life as reported in randomized trials. To date no medical treatment is proven effective nor devoid from deleterious effects and licenced for this indication.