Hemolysis is a rare complication of cytomegalovirus infection in the immunocompetent adult, and the mechanisms responsible for it remain obscure. Guidelines for treatment have yet to be established, and the effectiveness of antiviral therapy has not been proven. In this report, an unusual case of primary cytomegalovirus infection manifested by severe hemolysis in an immunocompetent adult is presented. Treatment with ganciclovir (5 mg/kg b.i.d.) for 10 days and prednisolone (2 mg/kg/day) for more than 3 months suggests that both virological and immunological mechanisms are probably responsible for the hemolysis.