Patients with metastatic melanoma who expressed HLA-Cw0702 and whose tumors had demonstrable MAGE-A12 expression were immunized with the peptide MAGE-A12:170-178 administered subcutaneously in incomplete Freund's adjuvant (IFA). The peptide was administered either every week or every 3 weeks for 4 cycles. Patients were evaluated for toxicity and for immunologic and clinical response to peptide immunization. Pre-treatment fine needle aspirates were obtained to document MAGE-A12 expression for enrollment. MAGE-A12 mRNA was identified in 62% of specimens. Nine patients were selected for vaccination based on MAGE-A12 expression and the presence of HLA-Cw0702. The immune response was monitored both by tetrameric HLA-Cw*0702/MAGE-A12:170-178 complexes and by analysis of interferon-gamma mRNA transcription using a quantitative real-time polymerase chain reaction assay after peptide-specific stimulation. The samples consisted of circulating lymphocytes analyzed ex vivo or after 10 to 14 days of in vitro sensitization. One of 9 patients sustained an ongoing partial clinical response. No convincing evidence of enhancement of the systemic immune response against MAGE-A12:170-178 could be documented. Because of the modest immunological and clinical results, the present protocol has been discontinued as new routes of administration are being considered.