Asymmetric septal hypertrophy, or ASH, is a genetically determined myocardial disorder that is transmitted as an autosomal dominant trait. Disproportionate hypertrophy of the ventricular septum has also been observed and associated with certain congenital cardiac malformations. It is concluded that the results of this investigation indicate that while disproportionate ventricular septal thickening may occur in patients with a variety of congenital heart malformations, such a finding is not necessarily a manifestation of the disease spectrum of genetically determined ASH.