Fabry's disease results from deficient activity of the enzyme alpha-galactosidase A. Cardiac abnormalities result from glycosphingolipid deposition in the myocardium, valvular tissue, and vessel walls. A noninvasive method to examine these abnormalities would be useful in the evaluation of patients. We examined the echocardiograms of 32 patients, 25 hemizygous and seven heterozygous, for Fabry's disease. The aortic root diameter was measured in each hemizygote. In nine patients under 26 years it was 33.2 ± 1.2 mm. and in two it was dilated. In 16 patients over 26 years it was 38.8 ± 1.2 mm. (p < 0.01), and in 12 it was dilated. The left ventricular posterior wall was measured in the echocardiogram of 21 normotensive hemizygotes. The difference in thickness between nine patients under 26 years (9.6 ± 1.3 mm.) and 12 patients over 26 years (12.4 ± .07 mm.) was not statistically significant. Only two of the nine younger patients had left ventricular wall thickness greater than normal compared to eight of the 12 older patients. The mean left ventricular shortening fraction of 22 hemizygous patients was normal. One hemizygote had echocardiographic evidence of mitral valve prolapse. Four of the seven heterozygotes had normal echocardiograms. Among the other three, one had increased left ventricular wall thickness, a second had disproportionate ventricular septal thickness, and a third had both abnormalities. The echocardiographic aortic root size was normal in each heterozygote. Abnormal echocardiographic findings were more common in older hemizygous patients, a distribution similar to that of the age of onset of cardiac dysfunction. Increased left ventricular wall thickness probably reflects glycosphingolipid deposition in the myocardium. Dilatation of the aortic root may result from degenerative changes of the aortic media. Abnormalities of mitral valve echoes were uncommon.