Epidemiological study in Akita City revealed that the Japanese prevalence of dilated cardiomyopathy was 12.5 per 100,000 population at the end of 1994, and the mean age of patients with dilated cardiomyopathy was 63 +/- 12 years. The prevalence was comparable with that of 9.03 per 100,000 population in Niigata Prefecture and with that of 15 per 100,000 population by the echocardiographic mass screening in 2,673 subjects from 12 Japanese rural areas. The prevalence of hypertrophic cardiomyopathy in Japan was 170 to 574 per 100,000 population by mass screening. In future, the genetic analysis may compensate the limitation of morphological diagnosis of cardiomyopathies and also reveal new aspects of these disorders.