Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality after bone marrow transplantation. Well-documented manifestations of GVHD include dermatologic, gastrointestinal, hepatic, pulmonary, musculoskeletal, and hematologic manifestations and sicca syndrome. To date, the heart has only rarely been reported to be a target of GVHD. We report a series of patients who developed bradycardia, coronary artery disease, or cardiomyolysis in association with acute or chronic GVHD. The severity of these manifestations ranged from asymptomatic to fatal. The bradycardias were responsive to increased immunosuppression. Although they are uncommon, it is important to recognize these cardiac manifestations, because they may reflect GVHD activity and may be reversible by increasing immunosuppression. © 2005 American Society for Blood and Marrow Transplantation.