The melanoma-associated antigen (MAGE) family consists of a number of antigens recognized by cytotoxic T lymphocytes. The MAGE genes were initially isolated from different kinds of tumors and, based on their virtually exclusive tumor-specific expression in adult tissues, they have been used as targets for cancer immunotherapy. MAGE genes encode for tumor-rejection antigens that are expressed in tumors of different histologic types and in normal testis and placenta. MAGE-B18 (melanoma-associated antigen B18) is a 343 amino acid protein that contains one MAGE domain and may be involved in tumorigenesis. The gene encoding MAGE-B18 maps to human chromosome X, which contains nearly 153 million base pairs and houses over 1,000 genes.