Targeted therapies against tumor biological properties are an essential part of individualized therapy concepts in breast cancer. Next to risk-adapted strategies using conventional chemo- and/or endocrine therapies, antibody therapy has become an additional option. The humanized monoclonal antibody trastuzumab (Herceptin) is the first novel targeted therapy approved for routine clinical application in advanced breast cancer. Patients with HER2/neu protein overexpression as assessed by immunohistochemistry (IHC) and/or gene amplification as assessed by fluorescence in-situ hybridization (FISH) in their tumors respond well to palliative trastuzumab therapy, either as single agent or in combination with chemotherapy. New combinations with endocrine therapy are currently being evaluated in clinical trials. Trastuzumab therapy is generally well-tolerated. So far, considerable cardiotoxicity was seen only in combination with doxorubicin. Thus, extensive cardiomonitoring is now performed in trials assessing further chemotherapeutic partners. Clinical trials looking at early trastuzumab therapy in the adjuvant (e.g. HERA, BOND 006) or neoadjuvant (e.g. TECHNO) setting are still open for recruitment in Germany. Since only about those 25 % of breast cancers which are HER2/neu-positive are eligible for trastuzumab, novel targeted therapeutics for the remaining HER2/neu-negative tumors are needed. Another therapeutic antibody, 2C4 (Pertuzumab, Omnitarg), is currently under clinical evaluation. It binds to a different epitope on HER2/neu than trastuzumab and inhibits heterodimerization with other HER receptors. Phase I data showed that 2C4 is well tolerated and clinically active.