In normal hearts, two-dimensional echocardiography from the apical window displays the left ventricular wall as a three-layered appearance (TLA): central bright layer and bilateral sonolucent zones. The TLA is considered to reflect the normal myocardial architecture: the predominant latitudinal fiber bundles of the midwall layer, and longitudinal or oblique ones on both sides. We analysed the TLA of the ventricular septum in 20 normal subjects, 20 patients with left ventricular hypertrophy due to pressure load (LVH), and 81 patients with hypertrophic cardiomyopathy (HCM). Of the 81 HCM patients, the layering was often obscure or absent in 53 (65%), whereas LVH patients showed clear TLA as well as normal hearts. In patients with severe layering disorder (n = 30), the age at diagnosis was lower (40 +/- 15 vs 50 +/- 12, p less than 0.05), and familial occurrence (53 vs 11%, p less than 0.01) and severe functional limitation (NYHA greater than or equal to III) were more common (27 vs 4%) than in those with clear TLA (n = 28). The disturbed layering detectable by echocardiography may reflect the disorder of basic myocardial fiber architecture in the ventricular septum, and is likely to become a useful marker of the pathologic severity of the disease.