This is a clinical report of a rare case of Charcot-Marie-Tooth disease associated with dilated cardiomyopathy. A seventy-seven-year-old Japanese male first visited our outpatient clinic with a ten-year history of muscular weakness in his bilateral lower extremities and gait disturbance characterized by classical features of peroneal muscular atrophy and inverted champagne bottle legs. Biopsy findings of the m. quadriceps femoris and the n. gastrocnemius revealed clustered atrophy of myofibrils and segmental demyelinization mingled with remyelinization. Because of his other problem of dilated cardiomyopathy, he had been treated with salt restriction, digitalis, diuretics and vasodilators, until his third hospitalization, when he developed terminal stage of severe congestive heart failure. Despite our intensive cardiac care, the patient died because of profound pump failure. Autopsy findings disclosed a remarkably dilated left ventricular chamber and an increased total heart weight of 600 grams. Grossly, the cross sectional view of the left ventricle revealed diffuse, but not homogenous fibrosis that was most prominent in the posterior wall. On light microscopic examination, the left ventricular myocardium revealed diffusely scattered muscular degeneration interlaced with fibrosis. Although large epicardial coronary arteries revealed only mild intimal atheromatous thickening, most of the small intramuscular coronary arteries were free from atherosclerosis. Neither diabetic nor amyloid lesions could be detected. It has been well known that cardiomyopathy is often associated with various forms of muscular dystrophy and Friedreich's ataxia.(ABSTRACT TRUNCATED AT 250 WORDS)