Despite significant advances in the administration of combination cytotoxic chemotherapy, the overall 5-year survival rate is about 75% for a woman who has node-positive breast cancer, and metastatic disease is considered incurable. Recent advances in our understanding of the immune system have led to the hope that manipulation of this organ system could be used as a cancer treatment. Strategies that have been used in the immune therapy of breast cancer include the administration of exogenous cytokines, vaccines, and humanized monoclonal antibodies (mAb). Each of these approaches is discussed in turn in this article.