The existence of familial cardiomyopathy as a clinical entity is confirmed. Three family groups of cardiomyopathy and postmortem findings are given. The histo-chemical abnormality in the cardiac muscle at necrospy has been described and consisted of presence of non metachromatic neutral pohysacchride which is suspected as an evidence of metabolic defect. In many cases no muco-polysacchride are recorded. The author concludes that aetiological agents may be various and may act singly or in com-bination in different cases.