We report two boys with chronic active Epstein-Barr virus infection (CAEBV) refractory to conventional chemotherapy, who received HLA-mismatched allografts of CD34-positive progenitor cells from their fathers. One patient developed veno-occlusive disease (VOD) of the liver on day 18 after transplantation and died on day 26. The other patient received the allograft during partial remission. Although he suffered recurrent infections due to Streptococcus viridans, he is now doing well 23 months after transplantation. CAEBV refractory to chemotherapy is considered to be a fatal EBV-infected T/NK-cell lymphoproliferative disease, and our experiences suggest that CD34-positive progenitor cell transplantation for patients with CAEBV lacking HLA-matched donors may be a feasible and useful treatment. However, the timing of transplantation is considered to be critical, and should be performed when the patient is in good clinical condition.