This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

1. To evaluate the efficacy of trastuzumab (a monoclonal antibody against HER‐2), given together with or following chemotherapy, in the adjuvant treatment of women with HER‐2 positive early breast cancer.
2. To evaluate the toxicity of trastuzumab when used as a adjuvant treatment of women with HER‐2 positive early breast cancer.