A 10-year-old girl developed recurrent bouts of massive hemoptysis over a 9-month period. No obvious bleeding source was detected. Her pulmonary angiogram showed a pulmonary aneurysm of the second branch of the left main pulmonary artery as well as widespread irregularities of the pulmonary arteries including areas of stenosis and pruning. Elective embolization of the aneurysm did not control hemoptysis and emergency left upper lobectomy had to be performed. Histology showed large artery wall injury with acute leucocytoclastic inflammation, fibrinoid necrosis, granulomatous inflammation, and ectasia of vessel wall. This combination of abnormalities has not been described to date and represents the first case of isolated pulmonary arteritis in children prior to puberty.