EBV-specific autologous CTL were grown in vitro from three adults (two liver transplant recipients and one patient on hemodialysis awaiting kidney retransplant). All CTL lines were TCR αβ, CD8 positive cells, EBV specific, and MHC class I restricted. The CTL lines were expanded in vitro and infused in three escalating doses (5× 10 7, 1× 10 8, and 2× 10 8) at monthly intervals. Weekly blood samples were collected following each infusion. EBV-specific CTL precursor cells in peripheral blood were quantitated by limiting dilution analysis, and their effect on EBV load in vivo was assessed by semiquantitative PCR. In all three patients, the numbers of CTL precursor cells increased during the weeks following the infusions and were highest after the third infusion. This level gradually declined but remained above the preinfusion levels for up to 3 mo. EBV genome copy number, on the other hand, dropped following the first infusion and became undetectable thereafter. The EBV DNA level remained lower than the pretransplant level in all patients for up to 3 mo after the last infusion. Our study shows that it is feasible to generate and expand EBV-specific CTL from pretransplant blood samples of solid organ transplant recipients, that these CTL can be stored and infused posttransplant, and that they remain cytotoxic and EBV specific in vivo. The aim of this study is to use these CTL for prevention and treatment of lymphoproliferative disease in solid organ transplant recipients.