Adoptive immunotherapy using autologous Epstein-Barr virus (EBV)-specific cytotoxic T-lymphocytes (auto-CTL) can regress posttransplant lymphoproliferative disorders (PTLD). Widespread applicability of auto-CTL remains constrained. Generation is time-consuming, and auto-CTL cannot be established in patients treated with the B-cell depleting antibody rituximab. By contrast, pregenerated allogeneic CTL (allo-CTL) offers immediate accessibility. Allo-CTL has previously shown efficacy in “early” polyclonal- PTLD. We treated three patients with aggressive, advanced monoclonal-PTLD following solid-organ transplantation. All were refractory to at least three prior therapies. Despite HLA disparity, there was negligible toxicity, with early in vivo antiviral efficacy and reconstitution of EBV peptide-specific immunity. Two patients attained complete remission (CR). One remains in CR 17 months following therapy, coincident with persistence of donor-derived tumor targeted EBV-specific CTL; the other died of non-PTLD related pathology. In the third patient, autopsy demonstrated homing of allo-CTL at the tumor site. Larger prospective studies of EBV-specific allo-CTL in PTLD are warranted.