The aim of this review is to examine the evidence available supporting the use of the docetaxel plus trastuzumab combination for patients with HER-2-positive metastatic breast cancer. The results of trials involving this combination are summarized, with an emphasis on efficacy and cardiotoxicity data. Finally, this article attempts to identify areas of uncertainty where new trials are warranted to improve our knowledge regarding optimal care for patients with HER-2-positive metastatic breast cancer.