A remarkable advance in tumor immunology during the last decade is the elucidation of the antigenic basis of tumor recognition and destruction. A variety of tumor antigens have been identified using several strategies including conventional experiments and newly developed bioinformatics. Among these antigens, cancer/testis antigen (CT antigen) is considered to be the most promising target for immunotherapy by vaccination. Successful immunotherapy of tumors requires understanding of the natural relationship between the immune system and tumor in the status of differentiation, invasion and maturation. Continued progress in development of effective cancer vaccines depends on the identification of appropriate target antigens, the establishment of optimal immunization strategies without harmful autoimmune responses and the ability of manipulating tumor microenvironment to circumvent immune suppression and to augment the anti-tumor immune response.