First identified in the United States in 1999, West Nile virus caused approximately 3,500 infections in the late summer and fall of 2002. The virus is predominantly transmitted by mosquitoes, and the risk of infection through blood product transfusion is believed to be low. We present a case of West Nile virus encephalitis transmitted by red blood cell transfusion at the time of coronary artery bypass grafting that resulted in the patient's death. Individuals undergoing procedures with high blood product transfusion requirements, such as cardiac surgery or organ transplantation, may be at higher risk of this nosocomial infection during epidemics.