We report an autopsy case of a cardiomyopathy characterized by fatty replacement of the right ventricular myocardium and compare its clinical and histologic characteristics with those of the arrhythmogenic right ventricular cardiomyopathy. A 39-year old male died suddenly in a hospital room. He had an alcoholic cirrhosis with ascitis, but the clinical examination and the biology showed no abnormalities explaining the death. Histologically, in the right ventricle, large areas of cardiomyocytes were replaced by fat, but there was no fibrosis. In contrast, fibrosis is present in association with fat in arrhythmogenic right ventricular cardiomyopathy. Fatty replacement of the right ventricle is likely to be a distinct entity. Right ventricular failure has been shown to be a possible complication. Sudden death is probably rare and is likely to occur when other arrhythmogenic factors are associated.