BACKGROUND Cytomegalovirus (CMV) infection is an ongoing clinical problem in solid-organ transplantation (SOT). Pretransplant CMV serology is currently the only tool for assessing the risk of CMV infection, although cellular immune responses driven by CMV-specific CD4 and CD8 T lymphocytes are important for controlling viral replication. Therefore, the analysis of CMV-specific T cells may be useful for estimating the risk of infection. METHODS This is a prospective study of patients with kidney transplants and no prophylactic treatment for CMV replication. CD4 and CD8 T-cell responses to the major CMV pp65 and IE-1 antigens in 15 seropositive patients at intermediate risk of CMV infection were investigated, according to current algorithms. Intracellular flow cytometry was employed to determine IFN-γ production as a functional readout. The response was analyzed in pretransplant samples and prospectively at 1 and 6 months and at 1 year posttransplant. RESULTS It was observed that the CD8 responses to IE-1 antigen were practically absent pretransplant in patients who developed CMV infection posttransplant. Within the group of patients free of infection, CD8 responses to IE-1 were detected more frequently and were significantly higher (P=0.0083). In a receiver operating characteristics curve analysis (AUC=0.929; P=0.010; 95% CI: 0.078-1.0), low CD8 responses to IE-1 (≤0.05%) pretransplant predicted the development of CMV infection under the immunosuppressive regime after transplant with 100% specificity and 85.7% sensitivity. CONCLUSIONS Assessment of IE-1-specific CD8 T-cell frequencies pretransplant may be a useful tool for identifying seropositive SOT patients at risk of developing CMV infection posttransplant.