A large array of antigens that are recognized by tumor-specific T cells has been identified and shown to be generated through various processes. We describe a new mechanism underlying T cell recognition of melanoma cells, which involves the generation of a major histocompatibility complex class I-restricted epitope after tumor-mediated uptake and processing of an extracellular protein--a process referred to as cross-presentation-which is believed to be restricted to immune cells. We show that melanoma cells cross-present, in an alpha v beta3-dependent manner, an antigen derived from secreted matrix metalloproteinase-2 (MMP-2) to human leukocyte antigen A*0201-restricted T cells. Because MMP-2 activity is critical for melanoma progression, the MMP-2 peptide should be cross-presented by most progressing melanomas and represents a unique antigen for vaccine therapy of these tumors.