To ascertain relationships between modes of death and various pathological parameters in hypertrophic cardiomyopathy (HCM), quantitative analysis of the disarray, fibrosis, and size of myocytes was performed in 22 autopsied subjects with HCM. According to mode of death, the subjects were categorized as three groups; (1) a sudden death group (10 patients), (2) a heart failure group (7 patients) and (3) a control group (5 patients). The group consisted of patients with HCM who were over 55 years old and who died of other diseases (e.g., cancer 3) or from accidents. The hearts were fixed in 10% formalin and sectioned from the base to the apex at 1 cm intervals. A section with maximal septal hypertrophy was histologically examined. The histologic findings in the interventricular septum (VS) and the left ventricular free wall (FW) were quantitatively analyzed using an image analyzer (Olympus VIP-21). The extents of fibrosis and disarray were greater in the sudden death group (fibrosis: VS/FW = 16 + 3/11 + 5%, disarray: VS/FW = 58 + 18/32 + 17%) than in the control group (fibrosis: VS/FW = 7 + 2/6 + 4%; disarray: VS/FW = 24 + 7/8 + 6%), but there were no significant differences in the various parameters of hypertrophy (heart weight, wall thickness, degree of asymmetric septal hypertrophy and size of myocytes) between these two groups. The heart failure group consisted of four hearts with dilated LV cavities and two hearts with small LV cavities. The former showed extensive replacement fibrosis (VS/FW = 37 + 7/25 + 5%) and disarray of residual myocytes (VS/FW = 20 + 16/14 + 6%).(ABSTRACT TRUNCATED AT 250 WORDS)