A cytomegalovirus seronegative 9 year-old child, affected by terminal dilated cardiomyopathy, underwent cardiac transplantation and received the heart of a cytomegalovirus seropositive donor. After the positive outcome of an acute moderate rejection episode which was treated with steroids, the patient developed an infectious clinical syndrome with cytomegalovirus seroconversion and virus isolation from peripheral blood leukocytes. The 5th endomyocardial biopsy showed a typical cytomegalovirus-like nuclear inclusion in a single cell. In spite of specific treatment with (9-(2-hydroxy-1-(hydroxymethyl)ethoxy)methyl-guanine) (BW B759U) (Wellcome), the patient died 45 days after the operation from cytomegalovirus-induced interstitial pneumonia and virus-associated hemophagocytic syndrome.