A case is reported of hypoplasie of the right ventricle with a wide atrial septal defect in a child of 10. The presence of cyanosis with right atrial and left ventricular preponderance led us to suspect tricuspid atresia, but this was excluded by catheterisation and angiocardiography. There was definitely and atrial septal defect with a two-directional shunt, but the tricuspid valve could be negotiated, and the right-sided opacity provided the essential diagnostic criterion, namely hypoplasia of the sinus portion of the right ventricle with a normal infundibulum. 17 other published cases of hypoplasia of the right ventricle with atrial septal defect are reviewed. The current indications for surgery are discussed in the light of the nature of the disordered physiology. Simple closure of the atrial septal defect, which was carried out successfully in 3 cases, appears to be of great value in the larger child, when there is a wide defect.