Congenital heart defects (CHDs) are thought to result from genetic and environmental factors that disturb cardiac embryogenesis. Because families with multiple members affected with atrial septal defects (ASDs) and atrioventricular canal defects (AVCDs) have been described in previous studies, and the paramembranous ventricular septum is in part completed by the formation of the atrioventricular cushions, this project describes a genetic-epidemiologic study of ASDs, paramembranous ventricular septal defects (VSDs), and AVCDs