Cytotoxic T lymphocyte (CTL) clones directed against autologous renal-cell carcinoma (RCC) cell lines were generated by mixed lymphocyteltumor-cell culture (MLTC) using peripheral blood lymphocytes (PBL). A CD8+, C W -CTL clone MZI257-CTL 5/30 with high cytolytic act-kity for the autologous tumor cell line MZI257-RCC was established. No lysis of the autologous EBV-transformed 6 lymphocytes (EBV-B) or K562 cells was observed. A panel of HLA-=-matched allogeneic RCC lines was recognized by CTL 5/30. Further specificity analysis showed a cross-reactivity with HLA-A2-matched allogeneic tumor cells of various origins, especially melanoma. CTL 5/30 was also cross-reactive with several HLA-A2-positive allogeneic normal kidney cells in culture. The restriction element identified for CTL 5/30 was HLA-A2, as shown by blocking of cytotoxicity using an anti-HLA-AZ monoclonal antibody (MAb) and by resistance of an HULA2-negative melanoma variant SK29-MEL. I .22 against I r i s by CTL 5/30. In this report we demonstrate HIA-AZ-restricted recognition of a T-cell-defined anti- gen on autologous renal-cancer cells. This antigen is also expressed and recognized in association with HLA-AZ on normal kidney cells in culture and other HLA-AZ-positive tumor cells. It may therefore be a normal differentiation antigen to which tolerance is incomplete in the renal-cell cancer system investigated.