We report a case of fatal primary herpes simplex virus type-2 (HSV-2) infection following liver transplantation, which manifested with fever and liver failure in the absence of muco-cutaneous disease. The infection was characterized by high levels of HSV DNA in blood and the patient's inability to mount HSV-specific T-cell responses while showing preserved T-cell responses against cytomegalovirus. The donor was HSV-1 immunoglobulin G (IgG) seronegative and HSV-2 IgG seropositive, whereas the recipient was HSV-1 and HSV-2 IgG seronegative, suggesting that the graft may have been the source of the infection. In HSV-seronegative recipients of grafts from HSV-seropositive donors, HSV infection should be included in the differential diagnosis of a febrile illness, regardless of the absence of muco-cutaneous disease. In this setting, real-time polymerase chain reaction applied to blood samples provides a sensitive, rapid, and quantitative diagnostic tool.