Cytomegalovirus infection was for many years one of the major complications of allogeneic bone marrow transplantation. During the past few years there have been major advances in the management of patients at risk for cytomegalovirus disease, and there are now several strategies that can be used. Antiviral prophylaxis has improved considerably and there are now three antiviral agents that can be used. Immunoprophylaxis by infusion of specific cytotoxic T cells is now feasible. The development of techniques for rapid diagnosis of cytomegalovirus infection including the antigenemia assay and the polymerase chain reaction for detection of cytomegalovirus DNA have made the use of preemptive therapy an attractive strategy. The outcome of therapy of cytomegalovirus pneumonia is still poor, with a survival of only approximately 50%, despite use of the combination of ganciclovir and high-dose immunoglobulin.