“…Several previous studies have noted the surprising lack of concordance for congenital heart malformations in monozygotic twins (Uchida and Rowe, 1957;Nora et al, 1967;Anderson, 1976). The purpose of this communication is to report a unique pair of monozygotic twins in whom secundum atrial septal defect, aneurysm of the membraneous ventricular septum, and frontal plane electrocardiographic left axis deviation were identified in each patient.…”