Human CTL have been isolated that show self-restricted recognition of autologous lymphoblastoid cell lines and allorecognition. The lymphoblastoid cell line ligand most likely used a peptide that is expressed in EBV-bearing cells when the virus enters the lytic cycle. This peptide is presented to CD8+ CTL by HLA-Cw7 molecules. The allogeneic ligand recognized on non-EBV-infected cells is composed of a class I glycoprotein and a naturally selected self-peptide. In previous studies we demonstrated that this ligand is determined by two MHC-linked genes: one gene encodes the allogeneic class I molecule whereas the other controls the self-peptide. Despite the use of different peptides and different class I molecules, seemingly equivalent structures are formed that enable these two ligands to function as antigenic mimics of each other. CTL with the same patterns of dual specificity could be isolated from four unrelated donors, indicating that HLA-Cw7 is frequently involved in self-restricted recognition of EBV-harboring cells. Such CTL could help not only to contain lytic virus during a primary infection but also may be maintained life-long to eliminate cells in which reactivated virus appears.