Ventricular ejection fraction was evaluated in a 30-year-old man. At birth he underwent a Rashkind procedure and placement of a Waterston shunt, followed by a Mustard procedure at age 2 years. In the Mustard procedure, an oblique right atriotomy is created, the atrial septum is excised, a pericardial baffle is sutured to incorporate the pulmonary veins into the right atrium, and another baffle is sutured to direct superior vena cava and inferior vena cava return into the left atrium and mitral valve. Radionuclide ventriculography showed that the systemic ventricle was the enlarged anatomic right ventricle. The systemic atrium is the anatomic right atrium and the pulmonary atrium is the anatomic left atrium. The ejection fraction of the right ventricle was estimated to be 32%.