Sir.—In a prospective study in the Journal by Betts et al (131:759-763, 1977) on 77 renal transplant recipients, it was found that primary cytomegalovirus (CMV) infection rather than reactivation of a latent CMV infection was associated with clinically apparent illness. The CMV posttransplantation syndrome consisted of prolonged fever, pneumonia, and mild hepatitis. Primary EpsteinBarr virus (EBV) infection after renal transplantation rarely occurs in adults because older allograft recipients have already experienced their initial infection with this virus in childhood. Reactivation of EBV infection seems to be a more common event, although the incidence among different series ranges from 2% to 56%.1-5 One reason for this great variation has been pointed out by Strauch et al4 who demonstrated that EBV reactivation may be associated with excretion of virus in the throat without elevation of antibody (antiviral capsid antigen). Reactivation has not been accompanied by a heterophil antibody response