Graft‐versus‐host disease (GVHD) is a frequent cause of morbidity and mortality after bone marrow transplantation. Acute GVHD most commonly involves the skin, gastrointestinal tract, and liver. Involvement of other organ systems is rare and remains controversial. We report a patient with GVHD who suffered a fatal ventricular arrhythmia shortly after bone marrow transplantation. Autopsy of the heart showed lymphocyte infiltration. Investigations for cardiotrophic viruses were negative, and chimerism analysis of the heart showed both donor and recipient DNA. We conclude that the cause of death was possibly graft‐versus‐host disease of the heart. A review of the literature revealed a total of 14 cases of possible cardiac GVHD. All but one of the reported cases have occurred in pediatric patients and six of those patients died, suggesting that this may be a rare but frequently fatal complication of pediatric allogeneic stem cell transplant. Pediatr Blood Cancer 2006; 47:624–628. © 2005 Wiley‐Liss, Inc.