Successful orthotopic heart transplantation was performed in a 38-day-old child with a fetal echocardiographic diagnosis of a left ventricular mass and in a 40-year-old woman with cardiac murmur since childhood and an echocardiographic diagnosis of asymmetric septal hypertrophy. Pathologic examination of the removed hearts, consisting of gross, histologic, immunohistochemical, and ultrastructural studies, led to the final diagnosis of cardiac fibroma. Both patients were alive and in good condition at 35 and 28 months, respectively, after operation.