Three cases of unilateral pulmonary vein atresia in children are described. The findings in all three cases were similar and consisted of hemoptysis, recurrent pulmonary infections, and a normal size or small lung with reticular markings. In combination, these findings should allow one to strongly suspect the diagnosis which then can be confirmed with radionuclide perfusion studies and pulmonary angiography. Both procedures demonstrate decreased blood flow to the involved lung, but the pulmonary arteriogram is the definitive study in that it shows a small pulmonary artery, pruned peripheral branches, stasis of contrast material, and nonvisualization of draining pulmonary veins. The condition generally is believed to be congenital and related to the somewhat more common, but still rare, focal congenital pulmonary vein stenosis. Treatment consists of surgical removal of the involved lung or lobe.