Arrhythmogenic right ventricular cardiomyopathy or dysplasia, a heart muscle disease of unknown cause, is anatomically characterized by variable replacement of myocardial muscle with adipose or fibroadipose tissue. It is usually considered a selective disorder whereas concomitant left ventricular involvement has been noted in a few cases. Two cases of the disease with evidence of extensive left ventricular involvement at pathologic examination are described. Hearts from two patients who died suddenly showed extensive biventricular infiltration by fibrofatty tissue in the first case and exclusively in the wall of the left ventricle the localization of the fatty and fibrotic lesions. These findings might suggest that the various localizations of the fibroadipose tissue are rather different expressions of the same disease and it is preferable to be termed 'arrhythmogenic cardiomyopathy' as other studies also indicate.