The realization that tumor cells utilize multiple mechanisms to escape from immune recognition and destruction has stimulated interest in developing and applying immunotherapeutic strategies which target both humoral and cellular immunity to malignant cells. As a result, the tumor-associated antigens (TAA) used as targets have to be expressed on the cell surface membrane of malignant cells. Furthermore, since most of the TAA used for active specific immunotherapy are self-antigens, a challenge facing tumor immunologists is to develop strategies which are effective in breaking tolerance to self-antigens. This chapter describes one strategy which relies on the use of peptide mimics of the human high molecular weight-melanoma associated antigen (HMW-MAA) as immunogens to implement active specific immunotherapy in patients with malignant melanoma. These mimics, which are isolated from phage display peptide libraries by panning with anti-HMW-MAA monoclonal antibodies, are expected to induce both humoral and cellular anti-HMW-MAA immunity.