The epidemiology of infections with 5 human herpesviruses (HHVs) (HHV-6, HHV-7, HHV-8, varicella zoster virus [VZV], and Epstein-Barr virus [EBV]) was investigated during the first year after solid organ transplantation in 263 patients who received oral ganciclovir or valganciclovir prophylaxis. HHV-6B DNAemia was uncommon, HHV-6A DNAemia was not observed, and HHV-7 DNAemia was prevalent. HHV-6 and HHV-7 DNAemia were not significantly associated with cytomegalovirus (CMV) disease, although a trend toward higher incidence of CMV disease was observed in HHV-6 DNAemic patients. VZV and HHV-8 DNAemia were not detected. EBV infection was common, although incidence of high-level EBV DNAemia was low, especially in patients who received valganciclovir prophylaxis. EBV-related posttransplant lymphoproliferative disease was not observed up to 12 months after transplantation. Compared with historic data, data from the present study suggest that antiviral prophylaxis may lower the incidence, prevalence, or level of DNAemia for infection with HHV-6, HHV-8, VZV, and EBV but not for infection with HHV-7.