Uhl's anomaly and arrhythmogenic right ventricular dysplasia are characterized by an analogous morphologic lesion which can be attributed to a major or minor expression of the same genetic disorder. The clinical diagnosis of arrhythmogenic dysplasia is not always easily established. A 23-year-old patient is discussed who showed extrasystolic arrhythmia, electrocardiographic signs of myocardial impairment and syncopes, the latter proving fatal. The segmental absence of myocardial tissue in the right ventricle is associated with interstitial sclerosis of the left ventricular myocardium. Subsisting myocardial fibers might be at the origin of a conduction slowdown creating an intraventricular reentry mechanism. The diagnosis should be considered in young subjects, more frequently males, with some years' history of palpitations, malaise with or without syncopes, and nonspecific electrocardiographic signs such as retarded activation of right cavities (S wave in derivations I and V6, possible right bundle block) and, during ventricular tachycardia, signs of delayed activation of left chambers, a right axis or an extreme deviation to the left.