Four children, aged 1 to 3 1/2, were first seen with cor pulmonale, pulmonary edema and severe respiratory distress due to chronic upper airway obstruction secondary to adenoidal or tonsillar hypertrophy or both. Arterial blood gas values, electrocardiograms and chest x-ray films were compatible with cor pulmonale. Echocardiography (four cases) and radionuclide angiography (two cases) showed severe right ventricular and right atrial dilation with reduced right ventricular ejection fraction. Following surgery, all four children improved; their echocardiographic and radionuclide findings returned to normal. Cardiac catheterization, traditionally performed in such cases, was unnecessary. The diagnosis and follow-up of this syndrome are adequately performed noninvasively.