A 46-year-old man with Fabry's disease having aortic regurgitation and complete atrioventricular (AV) block was presented. In spite of severe aortic regurgitation (Seller's grade 3/4), his two-dimensional (2-D) echocardiogram revealed increased thickness of the left ventricular wall with mild dilatation. The myocardial echo showed a fine granular sparkling texture suggesting phospholipid deposition in the myocardial tissue. The membranous portion of the interventricular septum was thickened, and the aortic valve was thickened and had imperfect coaptation. Endomyocardial biopsy of the right side of the interventricular septum revealed intramyocardial vacuolization by light microscopy. Electron microscopy confirmed the presence of myelinoid lamellar inclusion. Electrophysiologic examination revealed an intra-Hissian AV block. A DDD pacemaker was implanted and the patient's symptoms were improved. Valvular replacement was not attempted due to the danger of suture failure. The patient's brother (41-year-old) also had increased thickness of his left ventricular wall on echocardiography, and a complete AV block by ECG, but no valvular abnormalities. His sister (45-year-old) had increased thickness of the left ventricular wall on echocardiography, and negative T waves by ECG, but she had no cardiac symptoms. The possibility of cardiac involvement in this heterozygous woman with Fabry's disease should also be considered. The patient's 38-year-old sister and all the children of all family members had normal left ventricular wall thicknesses and normal ECG. These findings may correspond to the age-related disease severity. The possibility of cardiac abnormalities should be considered in heterozygous women with Fabry's disease.