A better understanding of immune recognition of cells has led to identification of potential new targets on tumor cells. Noticeable successes in melanoma have been immunization with the GM2 ganglioside vaccine, and the identification of novel antigens such as MAGE, BAGE and GAGE recognized by T cells cloned from cancer patients with regressing disease. However, the unexpected finding that other antigens recognized by these T cells were overexpressed normal differentiation antigens such as tyrosinase. Pmel 17 and Melan A have led to vaccines developed against differentiation antigens expressed in other solid tumors. Monoclonal antibody, anti-idiotype and antigen based vaccines for colorectal target antigens 17-1A, CEA and 791Tgp72 are all in clinical development. Similarly HER2/neu and mucin overexpression in breast cancer represent promising targets. Mutations in tumor oncogenes or suppressor genes which lead to malignant transformation can also present tumor-specific antigens. The most effective vaccines against infectious disease are live viruses. The development of DNA vaccines which act like viruses in entering cells and show continuous production of antigens offers great potential for the future.