This article reviews clinical data on adjuvant trastuzumab (Herceptin®, Genentech, Inc.) for patients with HER2-positive early breast cancer. Published articles were searched via PubMed (1985-2009), and abstracts were located from meeting books or search engines of congress Web sites (1994-2009). Search terms included breast neoplasms, breast cancer, breast tumor, or breast tumour and adjuvant plus HER2-positive plus trastuzumab. Trastuzumab improves clinical outcomes as well as disease-free and overall survival for patients with early HER2-positive breast cancer compared with adjuvant chemotherapy alone in this population. Trastuzumab has a favorable safety profile; levels of cardiac dysfunction were acceptable in all adjuvant trials, and cardiac dysfunction was manageable in most cases. Awareness of the clinical data will help nurses identify patients eligible for adjuvant trastuzumab, familiarize them with treatment and cardiac monitoring plans, and provide them with information to help advise, treat, and support patients from diagnosis through completion of therapy.