Epstein-Barr virus serology was performed before and after transplantation in 116 patients of a total series of 261 pediatric OLT recipients. Thirty-nine percent had no immunity before OLT, but this percentage decreased to 11.2% at 6 months and 10.5% at 2 years after transplantation. In this series, 10 children developed a B cell lymphoproliferative disease. Four had adenotonsillar involvement, 2 of them with associated digestive tract invasion. Three of these are alive, 2 after retransplantation for chronic rejection subsequent to arrest of immunosuppression. The fourth died from bone marrow aplasia. Three patients with multiorgan involvement died from multisystemic failure. The remaining 3 patients had a pseudotumoral mass. Two of these are alive, 1 after retransplantation for hepatic localization and secondary vascular and biliary complication. The last died from cachexia. Four patients developed the syndrome after viral reactivation, and 6 after primo infection. Four patients were under FK506 rescue therapy. We conclude that a high rate of EBV primo infection is observed in the first months after transplantation. A significant percentage will develop EBV-associated lymphoproliferative disease, which causes death in half of the patients, including all these with multiorgan involvement. Half of the patients may survive, but because immunosuppression must be stopped, retransplantation for chronic rejection is often necessary in survivors.