Five years of adjuvant therapy with anti-estrogens reduce the incidence of disease progression by about 50% in estrogen receptor-positive breast cancer patients, but late relapse can still occur after anti-estrogens have been discontinued. In these patients, excessive androgen production may account for renewed excessive estrogen formation and increased risks of late relapse. In the 50% of patients who do not benefit with anti-estrogens, the effect of therapy is limited by de novo or acquired resistance to treatment. Androgen receptor and epidermal growth factor receptor overexpression are recognized mechanisms of endocrine resistance suggesting the involvement of androgens as activators of the androgen receptor pathway and as stimulators of epidermal growth factor synthesis and function. Data from a series of prospective studies on operable breast cancer patients, showing high serum testosterone levels are associated to increased risk of recurrence, provide further support to a role for androgens in breast cancer progression. According to the above reported evidence, we proposed to counteract excessive androgen production in the adjuvant setting of estrogen receptor-positive patients and suggested selecting postmenopausal patients with elevated levels of serum testosterone, marker of ovarian hyperandrogenemia, for adjuvant treatment with a gonadotropins-releasing hormone analogue (medical oophorectomy) in addition to standard therapy with anti-estrogens. The proposed approach provides an attempt of personalized medicine that needs to be further investigated in clinical trials.