Prophylaxis has dramatically decreased the occurrence of cytomegalovirus (CMV) infection after renal transplantation. Optimal regimens of treatment remain controversial, especially in pediatric recipients. The aim of this study was to evaluate the effectiveness of valganciclovir (VGC) versus aciclovir/valaciclovir (ACV) in a pediatric renal transplant population. Data from 101 renal transplantations were retrospectively analyzed. Except those with R-/Dstatus, all patients received prophylaxis either with ACV, n = 39 or VGC, n = 38. Incidences of positive CMV antigenemia and disease, as well as the delay in relation to the prophylaxis, were collected during at least 12 months after the end of treatment. Positive CMV antigenemia was reported in 34 patients (ACV: 16, VGC: 16, no prophylaxis: 2). CMV disease occurred in 15 patients (ACV: 5; VGC: 8) (ns). For the majority of patients under VGC, positive CMV antigenemia occurred within the year following the withdrawal of prophylaxis (VGC: 14; ACV: 5, P <0.05), whereas it occurred during prophylaxis in 11 patients under ACV versus two under VGC (P <0.05). The over-all incidence of positive CMV antigenemia was similar between ACV and VGC prophylaxis. However, VGC was more efficient to prevent early CMV infection while patients treated with ACV had less CMV infection or disease after the end of the prophylaxis.