The frequency of right ventricular dysplasia (RVD) in an autopsy series of young persons with sudden cardiac death in the United States has not been previously reported. We reviewed the autopsies from cases of sudden cardiac deaths in young adults in the state of Maryland and noted three cases of RVD among 547 cardiac deaths (0.55%). These three cases of RVD in young adults and three additional cases from our file are presented. Their ages ranged from 19 to 28 yr, and there were five males and one female. Five deaths occurred during strenuous exercise while the sixth was unwitnessed. Three of these cases had a documented history of arrhythmias and 1 had palpitations. In each case, autopsy revealed right ventricular dilatation with partial absence of the myocardium and extensive fatty infiltrates with and without fibrosis. In four cases, collections of chronic lymphocytic infiltrates were seen, of which two had associated myocyte necrosis. In one patient, the disease was familial, while in the remaining five it was sporadic, suggesting a nongenetic cause.