An autopsied patient who showed typical dilated cardiomyopathy (DCM)-like features and was pathologically diagnosed with hypertrophic cardiomyopathy (HCM) is presented. The patient, a 60-year-old male at the time of death, died of intractable congestive heart failure. At autopsy the heart weighed 570g and showed marked left ventricular (LV) dilatation with a thin wall (ventricular septum/free wall of the LV = 7 mm/8 mm). There was no evidence of significant stenosis in the extramural coronary arteries. Massive fibrosis was found in the middle and outer thirds of the ventricular septum and anterior wall of the LV (48% in the ventricular septum and 9% in the free wall of the LV). As myocytes were not present in the area with massive fibrosis, percent area of disarray was calculated excluding the area of massive fibrosis and found to be 30% in the ventricular septum. Based on the marked increase in the percent area of disarray, this case was diagnosed as HCM. The patient's 37-year-old son showed asymmetric septal hypertrophy on echocardiography (ventricular septum/posterior wall of the LV = 15 mm/11 mm), marked LV hypertrophy on electrocardiography, and diffuse and marked disarray by endomyocardial biopsy. There were also LV dilatation (LV diastolic dimension = 51 mm) and hypokinesis of the LV; as a result, a diagnosis of HCM with features of DCM was made.