To assess pathophysiological changes and prognoses in hypertrophic cardiomyopathy (HCM), the clinical courses of 190 patients with HCM between 1968 and 1985 were reviewed and analyzed. Their average follow-up period was 4.0 years. During the course of follow-up, 24 patients died of heart disease at annual mortality of 3.3%; 22 sudden death, and two congestive heart failure. Among the 190 cases, 70 were studied by echocardiography with an average follow-up period of 4.4 years. The subjects were categorized in three groups: 10 who died suddenly (SD group), 16 with ventricular tachycardia (VT group) and the remaining 44 without ventricular tachycardia (non-VT group). Initially, the VT group had significantly greater left ventricular end-diastolic dimension (LVDd), smaller % fractional shortening (FS), and normalized rapid felling rate (RFR) compared with the other two groups. However, there were no significant differences in the echocardiographic parameters between the SD and non-VT groups. During the follow-up period, no changes in echocardiographic parameters were observed in the non-VT group. However, LVDd was increased in both the SD and VT groups, and normalized RFR and atrial filling rate (AFR) were decreased in the SD group. These results suggested that close observations using echocardiography are useful for evaluating the natural history and prognoses of HCM.