Based on the known epidemiology of cytomegalovirus (CMV) infection, primary infection among seronegative patients is preventable by use of seronegative blood products including marrow. A potential alternative is use of leukocyte-depleted blood products. Efficacy of passive immunoprophylaxis remains uncertain, and this modality cannot be recommended until additional studies are available. Antiviral agents can be used to suppress or delay CMV infection among seropositive patients who develop active infection from reactivation of latent virus. Intravenous acyclovir significantly reduced the probability of CMV infection and disease among seropositive patients in a controlled trial. The new antiviral agents ganciclovir and foscarnet may provide better results, although the marrow toxicity of ganciclovir may limit its utility. For treatment of CMV pneumonia the combination of ganciclovir and CMV immunoglobulin has shown promise in initial trials.