Experiments with mouse systems have shown that antigens recognized on tumors by cytolytic T lymphocytes can be the targets of immune responses that destroy the tumor cells without exerting harmful effects on normal tissues. in recent years, a number of genes that code for these antigens have been identified. The first gene studied, MAGE-1, coded for an antigen recognized by an autologous cytolytic T-cell clone. It belongs to a family comprising at least twelve members, but the function of the proteins encoded remains unknown. these genes have no expression in normal tissues (but testis and placenta); the tumoral peptides are presented to the immune system by specific HLA molecules. some other tumoral antigens are not restricted to tumors but appear on normal melanocytes (tryrosinase, gp100...). Knowing these genes opens new possibilities in specific cancer immunotherapy