Interruption of the inferior vena cava with azygos continuation is present in at least 65% of the patients suffering from left atrial isomerism (polysplenia syndrome). First-pass radionuclide angiography using a peripheral vein of the foot correctly diagnosed interruption of the inferior vena cava in seven patients. Four had azygos continuation to the right superior vena cava and in three it was to the left superior vena cava. In all the patients, cardiac catheterization confirmed the diagnosis. Four underwent surgical correction (or palliation), three are waiting for an operation. Radionuclide angiography is a simple outpatient procedure and useful in the clinical diagnosis of this syndrome.