One of the most recent advances in the management of Her-2/neu positive breast cancer is the validation of a targeted therapy from bench to the clinic, particularly towards the adjuvant setting. The recommended dose of trastuzumab (Herceptin), a humanized monoclonal antibody targeting the HER-2 antigen, has been determined in phase I studies. In the metastatic patients two randomised trials have demonstrated its efficacy when associated to taxanes. In less than 10 years, trastuzumab became the standard of care in the adjuvant treatment of HER-2/neu positive breast cancer. In this setting, two combinations regimen with chemotherapy (concomitant or sequential) have been recently published. The concomitant schedule has been used in three studies (North American Group, BCIRG, FinHer), whereas in the Hera trial trastuzumab was started after the end of neo-adjuvant and adjuvant chemotherapy. In this article, the advantages and uncertainties on efficacy and toxicities of the trastuzumab administration modalities, associated or not to chemotherapy and radiation therapy, are discussed.