Herpes virus infections, particularly those caused by cytomegalovirus (CMV), lead to significant and, sometimes severe, clinical problems for the immunocompromised host. As effective agents have become available, several treatment and prevention strategies have evolved over the past decade, first in intra-venous form and more recently, as oral preparations. Valganciclovir, the valine ester of ganciclovir, is an orally administered, potent, antiviral agent active against all herpes viruses. When taken orally, valganciclovir has much-improved bioavailability compared with oral ganciclovir and achieves ganciclovir exposures similar to intravenous ganciclovir. Clinical trials evaluating the safety and efficacy of valganciclovir for the treatment of new AIDS-associated CMV retinitis showed equivalency to intravenous ganciclovir and prevented progression of quiescent disease. In solid organ recipients, once-daily valganciclovir has been proven equivalent to oral ganciclovir for the prevention of CMV infection. The high bioavailability and convenient dosing formulation make valganciclovir an attractive option for these indications.