Executive SummaryCMV can be life-threatening for immunocompromised patients, including those with AIDS and those undergoing organ transplants or chemotherapy. In the bone marrow and solid organ transplant population, CMV can cause life-threatening pneumonia. In the AIDS patient population, retinitis caused by CMV is the primary cause of blindness.CMV is generally a very common viral infection. It is the most common viral infection known to be transmitted to the fetus during pregnancy and is the leading infectious cause of birth defects in the United States.CMV infections afflict the greatest number of AIDS patients after Pneumocystis carinii. The incidence for this infection in the US is estimated at approximately 18,000. There is a great deal of evidence that transmission of the virus is primarily cell to cell. Sexual transmission and perinatal transmission appear to be of epidemiological importance, as incidence rates are higher in young infants and young adults than they are in other age groups.The use of interferon in transplant recipients has reduced shedding of the virus and apparently improved the associated clinical conditions. The use of specific intravenous immunoglobulins with and without DHPG is associated with reduced CMV-associated symptoms in BMT.The FDA's approval of Varivax vaccine for varicella (chicken pox) in 1995 marked a milestone in the fight against herpes viral diseases. For the first time a vaccine had been shown to be effective in preventing a herpes virus infection, giving hope that vaccines could be developed for HSV, CMV, and other herpes viruses as well.