To clarify the influence of cardiac function of myocardial histologic lesions on the prognosis of hypertrophic cardiomyopathy (HCM), most recent echocardiographic findings of 30 deceased patients were reviewed. In 12 patients, histological sections from the left ventricular transverse plane made at necropsy were examined. According to the main causes of death, patients were categorized into four groups as sudden death (17 cases), heart failure death (four cases), embolic death (four cases), and non-cardiac death (five cases). 1. Clinically, atrial fibrillation and heart failure (NYHA III, IV) were frequently observed in heart failure and embolic groups. 2. Echocardiographically, left ventricular wall thickness did not differ among the four groups, but percent fractional shortening was significantly smaller in heart failure group than in non-cardiac group, and left ventricular end-diastolic dimension (LVDd) and left atrial dimension were significantly greater in heart failure group than in non-cardiac group. The normalized rapid filling rate was less in heart failure, embolic, sudden death and non-cardiac groups in that order. 3. Histopathologically, the mean myocyte diameter (MD) and percent area of disarray (%D) did not differ among the four groups, but % area of massive fibrosis (MF) greater than 2 mm2 was larger in heart failure, embolic, sudden death and non-cardiac groups in that order, especially in heart failure group. 4. Comparison of echocardiographic and histopathological findings: Though MD and %D did not correlate with any echocardiographic indices, %MF correlated significantly with LVDd (r = 0.83, p less than 0.005), and correlated inversely with the normalized rapid filling rate (r = -0.80, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)