Recently, chemoprevention trials have demonstrated the efficacy of preventive medical treatment (PMT) in reducing breast cancer (BC) detection rates in at-risk affected and unaffected women selected according to clinical and/or familial risk criteria, particularly with the use of tamoxifen (TAM). Major concerns limiting the routine use of TAM are the questionable benefit/risk ratio and poor patient compliance, which justify the studies undertaken to determine the efficacy of aromatase inhibitors (AIs) with respect to TAM. Issues such as therapy duration, impact on survival, incidence of side-effects and which subsets benefit most from treatment, still remain unsolved. Therefore, only ER+ BC patients are routinely subjected to PMT, independently of their BRCA1/2 status, using adjuvant hormonal therapy. More attention must be focused towards BRCA1/2 carriers as they are probably the women at highest risk of developing BC, in which available data remain controversial and in which hormone-therapy might be important. Hence, at-risk women (affected patients or unaffected women) should be carefully evaluated for inclusion into highly selected preventive clinical trials aimed at evaluating PMT independently of, or according to, BC predisposition status (unknown, positive or negative BRCA1/BRCA2 status) and with respect to menopausal status. BC patients, harboring a BRCA1/2 predisposition, may represent the best subset for extended adjuvant treatment, useful as PMT, simultaneously. Only the evolving differentiation of categories of at-risk women will allow physicians to discriminate PMT in a highly selective manner.