Antigens encoded by MAGE genes are of particular interest for cancer immunotherapy because of their strict tumoral specificity and because they are shared by many tumors. MAGE antigenic peptides are currently used in therapeutic vaccination trials. The identification of additional antigenic peptides is likely to be important for the future of these clinical trials in order to increase the number of patients eligible for these vaccinations and to analyze in detail the T-cell response of vaccinated patients. We describe here the isolation of a cytolytic T lymphocyte (CTL) clone which recognizes a new MAGE-A1 peptide, RVRFFFPSL (MAGE-A1(289-297)), which is presented by HLA-B7. This CTL clone lysed HLA-B7 tumor cells expressing MAGE-A1. HLA-B7 is expressed by approximately 20% of Caucasians