Knowledge of the immunodominant responses to Epstein‐Barr Virus (EBV) and human cytomegalovirus (HCMV) should help to generate cytotoxic T cell lines to these herpesviruses. Here we report on the analysis of CD8 T cell responses to EBV and HCMV in the blood of kidney transplant recipients undergoing viral reactivation (n = 16) and in healthy virus carriers (n = 10). We used a transient COS transfection assay that permits semi‐quantitative estimation of CD8⁺ T cell responses against a larger number of HLA / viral protein combinations within polyclonal T cell lines and thus allows a rapid identification of major epitopes. From the comparison of these responses to those that we previously described in the synovial fluid of patients suffering from various forms of chronic arthritis (n = 32), it appears that EBV‐specific T cells are mainly directed against a restricted set of immunodominant epitopes, primarily generated during the early lytic cycle and that both IE1 and pp65 are targets of the anti‐HCMV response. We suggest that this method could be generally applied to the rapid identification of immunodominant T cell epitopes in viral and tumor immunity, and could help selecting HLA‐peptide complexes that could be used to detect and sort specific T cell populations.