Arrhythmogenic right ventricular dysplasia (ARVD) is a new form of cardiomyopathy probably more frequent than commonly reported. The incidence is unknown. ARVD is a heart muscle disorder of unknown cause that is characterised pathologically by fibro-fatty replacement of the right ventricular myocardium. It is a rare but important cause of sudden cardiac death in young, otherwise healthy persons. The right ventricle should be extensively sampled histologically in all cases of sudden unexpected death, especially those that are exercise related. The disease is often familial (about 30%) with an autosomal dominant inheritance.