Echocardiography has been used for cardiovascular evaluation of individuals and families with Ullrich-Noonan syndrome. Previously undiagnosed left ventricular disease has been found as a discrete lesion or in association with other cardiac abnormalities. This raises the estimated frequency of heart disease in the Ullrich-Noonan syndrome to about 50%. Since left ventricular disease in this syndrome may not be entirely typical of asymmetric septal hypertrophy, caution should be exercised in the echocardiographic diagnosis. To date, one notable difference between the echocardiograms in these patients and other patients with asymmetric septal hypertrophy is the absence of systolic anterior motion of the mitral valve. Since the most common cardiac lesion the the Ullrich-Noonan syndrome is pulmonary stenosis, the potential for septal thickening produced by severe pulmonary stenosis must also be taken into account.