Hypertrophic cardiomyopathy (HCM) or idiopathic hypertrophic subaortic stenosis (IHSS) has been defined as an autosomal dominant myocardial disease characterized by specific physical findings, echocardiographic features, asymmetric septal hypertrophy and disordered myocardial architecture. Echocardiographic and scintiphotographic studies failed to reveal evidence of asymmetric septal hypertrophy in four patients with systolic anterior movement of the mitral valve and the typical ausculatory and peripheral pulse abnormalities characteristic of HCM. Postmortem examimination in one patient demonstrated mild concentric left ventricular hypertrophy and a normal arrangement of myocardial muscle fibers. These observations in four patients demonstrate that both systolic anterior movement of the mitral valve and the physical findings characteristic of HCM are not specific for the autosomal dominant myocardial disease characterized by asymmetric septal hypertrophy and abnormal septal histology.