Arrythmogenic ventricular dysplasia is a heart muscle disease characterized by a progressive muscular dystrophy of the right or left ventricle (usually the right) and an associated transmural deposit of adipose or fibroadipose tissue. The disease has an unknown cause but is believed to be a selective disorder usually involving the right ventricle, although there have been concomitant “minor” abnormalities of the left ventricle reported. Left ventricular involvement is considered less profound than right ventricular involvement. Any right, left, or biventricular involvement suggests different expressions of the same disease rather than separate diseases. In cases of sudden death, particularly involving younger adolescents, the role of arrhythmogenic ventricular dysplasia should not be overlooked. Figures, references