Patients with Holt–Oram syndrome frequently have atrial septal defect. Sinus venosus atrial septal defect is frequently associated with partial anomalous pulmonary venous return. Primum atrial septal defect is frequently associated with cleft mitral valve. Systolic ejection murmur not proceeded by ejection click plus fixed splitting of the second heart sound with or without middiastolic murmur over the left lower sternal border is pathognomonic of atrial septal defect. Heart size may be normal by chest X-ray in patients with atrial septal defect. Increase in pulmonary vascular markings on chest X-ray is frequent in patients with moderate and large atrial septal defects. Pulmonary vascular obstructive disease occurs in some patients with unrepaired atrial septal defect during the fourth decade of life or later.