Because the left upper lobe bronchus overlies the left pulmonary artery (PA), T2-3 lesions, N0-1 disease, or rarely inflammation may involve this vessel, necessitating lobectomy with partial PA resection or pneumonectomy with sacrifice of the lower lobe. In 486 operations performed for left upper lobe lesions between 1966 and 1992 (wedge, 111; segmentectomy, 131; lobectomy, 155; pneumonectomy, 89), isolated PA encroachment was caused by bronchogenic carcinoma (32), invasive aspergillosis (2), or organized pneumonitis (1) and occurred in 9% (32/360) of malignant left upper lobe tumors and 2% (3/126) of benign lesions. Initially (1966 through 1979), PA involvement was the indication for 30% (18/60) of left pneumonectomies. Later (1980 through 1990), tangential resection of the PA was attempted in 11, 5 ending up with pneumonectomy. Overall, 35 of 244 patients undergoing major left upper lobe resection (lobectomy or pneumonectomy) had PA encroachment. Recently, we have performed, selectively in patients with restricted lung function, six left upper lobectomies with sleeve resection of the PA. Paneled saphenous vein interposition was used (3) or 18-mm polytetrafluorethylene tube prostheses (3). All patients survived, 1 later requiring completion pneumonectomy for bronchostenosis after wedge bronchoplasty. Two have since died of metastases or pulmonary insufficiency; the remainder (average follow-up, 17 months) are asymptomatic with lower lobe function in 3 confirmed by differential ventilation-perfusion scans and pulmonary angiography.