AbstractAmong the human herpesviruses, cytomegalovirus (CMV) is the only one that has assumed significant importance in blood transfusion. Transfusion transmission of CMV (TT‐CMV) to seronegative immunocompromised patients can lead to lethal CMV disease. Studies over the past 30 years have demonstrated that monocytes latently infected with CMV represent the primary vector for TT‐CMV, and that TT‐CMV can be largely abrogated by transfusing at‐risk patients with either seronegative units or blood filtered to remove white blood cells. However, the small number of cases of breakthrough TT‐CMV that follow transfusion of either seronegative or filtered blood still produce morbidity and mortality. These circumstances have motivated ongoing efforts to provide improved protection from TT‐CMV, including the use of CMV DNA amplification for blood screening, and pathogen inactivation to sterilise all blood components prior to transfusion. Copyright © 2002 John Wiley & Sons, Ltd.