To assess specific cytotoxic T lymphocytes (CTLs) against Severe acute respiratory syndrome (SARS)-coronavirus, a modified DimerXflow cytometry assay was performed with peripheral blood mononuclear cell (PBMC) from HLA-A2+ SARS-recovered donors at differenttime points post disease. CD8+ DimerX-S1203+ CTLs were detected in the PBMC from these donors up to 3 months after recovery. Thepercentages of CD8+ DimerX-S1203+ cells paralleled the numbers of interferon-g-positive spots in an ELISPOT assay using the sameantigenic peptide. In conclusion, DimerX-based flow cytometry staining may prove to be a real-time method to screen for CTL directed atepitopes from a newly identified virus.