From peripheral blood mononuclear cells of a patient with renal cell carcinoma (RCC), we isolated several T-cell clones, which efficiently lyse the autologous RCC cell line (LE-8915-RCC), but not the autologous Epstein Barr virus-transformed lymphoblastoid cell line. Most of the cytotoxic T lymphocyte (CTL) clones recognize HLA-A-A1-positive allogeneic RCC cell lines, indicating that HLA-A1 is the restricting element for these T cells. One CTL clone exclusively recognizes the autologous tumor cells. The HLA-A1-restricted CTL clones can be divided further into two subsets of T-cell clones, one blocked by an HLA-A1-specific monoclonal antibody, the other not. The reactivity of HLA-A1-restricted T-cell clone 6/135 was studied in greater detail. This T-cell clone also recognizes a number of melanoma cell lines, indicating that expression of the antigen seen by this CTL clone is not restricted to RCC. Strikingly, the antigen is not exclusively expressed by tumor cell lines, because primary cultures of proximal tubulus epithelium cells, adult mesangial cells, and normal breast epithelium cells are also lysed. These results corroborate the notion that renal carcinoma cells are immunogenic by virtue of a broadly distributed antigenic structure that may serve as a target for cytotoxic T cells and may be a potential candidate for tumor vaccine development.