22. Zutter MM, Martin PJ, Sale GE, et al. Epstein-Barr-virus asso-ciated B cell lymphoproliferative disorders after bone marrowtransplantation. Blood 1988; 72: 520.23. Renard TH, Andrews WS, Foster ME. Relationship betweenOKT3 administration, EBV conversion, and the lymphoprolif-erative syndrome in pediatric liver transplant recipients.Transplant Proc 1991; 23: 1473.24. Davis CL, Harrison KL, McVicar JP, Forg PJ, Bronner MP,Marsh CL. Antiviral prophylaxis and the Epstein Barr virus-related post-transplant lymphoproliferative disorder. ClinTransplant 1995; 9: 53.25. Yao QY, Ogan P, Rowe M, Rickinson AB. Epstein-Barr-virustreated B cells persist in the circulation of aciclovir-treatedvirus carriers. Int J Cancer 1989; 43: 61.26. Kuo PC, Dafoe DC, Alfrey EJ, Sibley RK, Scandling JD. Post-transplant lymphoproliferative disorders and Epstein-Barr vi-rus prophylaxis. Transplantation 1995; 59: 135.27. Darenkov IA, Marcarelli MA, Basadonna GP, et al. Reducedincidence of Epstein-Barr virus-associated posttransplant lym-phoproliferative disorder using preemptive antiviral therapy.Transplantation 1997; 64: 848.28. Neyts J, Andrei G, De Clercq E. The novel immunosuppressiveagent mycophenolate mofetil markedly potentiates the anti-herpesvirus activities of aciclovir, ganciclovir and penciclovirin vitro and in vivo. Antimicrob Agents Chemother 1998; 42:216.29. Tressler RJ, Garvin LJ, Slate DL. Anti-tumor activity of myco-phenolate mofetil against human and mouse tumors in vivo.Int J Cancer 1994; 57: 568.30. Fleiss JL. Statistical methods for rates and proportions, 2nd ed.New York: Wiley, 1981: 38.31. Alfrey EJ, Friedman AL, Grossman RA, et al. A recent decreasein the time to development of monomorphous and polymor-phous posttransplantlymphoproliferative disorder. Transplan-tation 1992; 54: 250.32. Ciancio G, Siquijor AP, Burke GW, et al. Post-transplant lym-phoproliferative disease in kidney transplant patients in thenew immunosuppressive era. Clin Transplant 1997; 11: 243.33. Morris RE. Transplantation. Beware: shifting paradigm ahead.Lancet 1996; 1 (suppl II): 26.Received 3 July 1998.Accepted 11 December 1998.