The rise of aromatase inhibitors changes our habits in hormonal treatment in breast cancer. In premenopausal women tamoxifen with ovarian suppression remains reference treatment although the succession of the two treatments has not been explored as far as treatment duration is concerned. In post menopausal women the use of AI in the first line treatment gives a greater chance of response and a longer response duration than tamoxifen with a good tolerance profile. When both treatments are used, total duration of endocrine therapy (time to chemotherapy) is significantly longer for patients who receive AI in first line than for patients who receive tamoxifen first. In adjuvant treatment, tamoxifen and ovarian suppression remain references in premenopausal patients; therefore trials using aromatase inhibitors with LH-RH agonists are running. In post menopausal women aromatase inhibitors are challenging tamoxifen. Three large trials proved their superiority over tamoxifen. In the adjuvant setting AI may represent a beneficial approach, they can be used up front or in sequence with tamoxifen. The ideal combination or sequence of therapies requires investigations. At last duration of hormonal treatment remains an open deal.