A healthy 33-year-old man presented with a short history of viral infection and recent petechiae. Examination of the blood showed a profound thrombocytopenia. He was diagnosed as having cytomegalovirus infection by serological examination. A high level of platelet-associated immunoglobulins was demonstrated suggesting an immune basis for the thrombocytopenia and we, therefore, treated the patient with bolus methylprednisolone and gamma-globulin, resulting in prompt recovery. Recognition for CMV-induced thrombocytopenia is important for early diagnosis.