Immunization with anti-idiotype (Id) antibodies represents a novel new approach to active immunotherapy. Extensive studies in animal tumor models have demonstrated the efficacy of anti-Id vaccines in preventing tumor growth and curing mice with established tumor. We have developed and characterized several murine monoclonal anti-Id antibodies (Ab2) which mimic distinct human tumor-associated antigens (TAA) and can be used as surrogate antigens for triggering active anti-tumor immunity in cancer patients. Encouraging results have been obtained in recent clinical trials. In this article, we will review the existing literature and summarize our own findings showing the potential of this approach for various human cancers. We will also discuss where anti-Id vaccines may perform better than traditional antigen vaccines.