We describe 3 siblings with muscular ventricular septal defects, two requiring surgical closure. One of their offspring had a rare congenital aneurysm of the muscular ventricular septum, also requiring surgery. Another had a small muscular ventricular septal defect which closed spontaneously. Their father had echocardiographic evidence suggestive of a closed muscular defect. Paternal cousins have had ventricular septal defect, hypertrophic cardiomyopathy, and tetralogy of Fallot. There was no evidence of 22q11 deletion. Although ventricular septal defects are the most common congenital heart defect, such familial clustering is uncommon. The distribution of cases in this family suggests autosomal dominant inheritance. With echocardiography, and more precise diagnosis of defects which close, a larger genetic component may be revealed in other families.