Pulmonary atresia with intact ventricular septum (PA/IVS) is a rare disease, accounting for less than 3% of all congenital heart lesions. The cause of PA/IVS is unknown. We report the occurrence of two first cousins with PA/IVS, suggestive of autosomal dominant inheritance with incomplete penetrance. The study of such families should ultimately lead to the identification of the gene(s) that cause congenital heart disease.