The bronchial artery supplies the tracheobronchial tree, the walls of the pulmonary artery and pulmonary vein, the visceral pleura, the mediastinal lymph nodes, and the nerves. The major portion of the bronchial arterial flow is drained into the pulmonary circulation through the bronchopulmonary communications. The remainder of the bronchial arterial flow is drained into the azygos and hemiazygos veins. The normal bronchial arterial flow is approximately 1% of the cardiac output; it may vary with the systemic arterial pressure and the partial pressures of oxygen and carbon dioxide. Certain chemical agents, eg, histamine and acetylcholine, increase bronchial blood flow, whereas epinephrine decreases it. The bronchial circulatory system hypertrophies in some congenital heart diseases, which may pose a problem during surgery for these conditions. The bronchial circulation is also known to increase in lung infections, pulmonary embolism, and primary lung cancers and this increase may be responsible for the hemoptysis seen in these conditions. The role of the bronchial circulation in lung-fluid balance is under investigation. Catheterization and occlusion of bronchial arteries has been performed to control massive and life-threatening hemoptysis.