The epidemiologic data on myocardial disease is relatively insufficient because of its rarity. The author tried to clarify its epidemiologic characteristics in autopsy cases during the 30 years of 1958-1987, using the Annuals of Pathological Autopsy Cases in Japan published annually by the Japanese Society of Pathology and to utilize the date for elucidation of pathogenesis of cardiomyopathy. I picked up cases with cardiomyopathies, including dilated (DCM), hypertrophic (HCM), restrictive or endomyocardial disease (EMD (R)) and unclassified (UCM) types, primary endocardial fibroelastosis (EFE), and myocarditis diagnosed as viral, idiopathic or nonspecific and made statistical analysis. The same analysis was made using selected cases under 15 years of age. There were 1,562 cases with DCM (0.21%), 458 with HCM (0.06%), 241 with EMD (R) (0.03%) and 714 with UCM (0.06%), 1207 with myocarditis (0.16%). The incidence of DCM, HCM and myocarditis began to increase from the latter half of the 1970's. The preponderance of males for DCM and that of females for myocarditis was found. Age distribution pattern of DCM and HCM showed two peaks in the young and middleaged groups in early years, but in recent years, the peaks shifted to 50-60's and to 60-70's, respectively. The complication of malignant neoplasms or nephrosclerosis in cases with HCM was more common than with DCM. The incidence of DCM was about three times higher in the adults than in the children, whereas those of HCM and myocarditis was almost equal in both groups. The annual change of incidence of cardiomyopathy and myocarditis in the children was closely related with each other. The fluctuation pattern of EFE was similar to that of myocarditis of all ages. These findings suggest that myocarditis is associated with cardiomyopathy in part and EFE as the pathogenesis or at least the cause of death.