An autopsy case of cardiac rhabdomyoma associated with tuberous sclerosis in a 27-day-old infant is presented. He was born with severe cyanosis. Echocardiogram revealed the presence of multiple mass lesions, some of which protruded into the left ventricle at the level of subaortic valve. From the age of 4 days, cardiac arrhythmia developed and lasted until his death. The arrhythmia started as WPW syndrome and atrial extrasystoles and then additional paroxysmal supraventricular tachycardia, ventricular fibrillation, sinus arrest, and S-A block occurred. Computed tomographic scanning of the brain revealed the presence of symmetric high-density spots around the central part of lateral ventricle. Before his death paroxysmal supraventricular tachycardia occurred frequently which changed to ventricular fibrillation and he collapsed without urination and then died. Autopsy examination revealed the presence of generalized congestion, multiple nodules of cardiac rhabdomyoma, some of which causing subaortic stenosis, and tuberous sclerosis in the brain. From the clinical and autopsy findings, the direct cause of death was attributable to the cardiac rhabdomyoma.