A genetic study of 119 correlative cases of patent ductus arteriosus has been performed. The isolated cases showed female predominance, but there was a three times higher risk for the sibs of male cases, suggesting a multifactorial causative mechanism. Dermatoglyphs presented an excess of arches in male, and a tendency to distal axial triradius in female. There were 15 cases belonging to polymalformative syndromes, such as mongolism, Turner, Noonan, Holt-Oram, Lewis and rubella embryopathy.