The pulmonary circulation is the part of the circulatory system, which transports deoxygenated blood away from the right ventricle of the heart to the lungs, and then returns the oxygenated blood to the left ventricle and atrium of the heart. The vessels involved in pulmonary circulation are pulmonary veins and pulmonary arteries. Pulmonary circulation can be affected by a number of conditions, chief among which are pulmonary hypertension, pulmonary embolus, vascular resistance, cardiac shunt and pulmonary shunt. Any disease that damages the lungs and affects their function may be called a chronic lung disease. It encompasses a number of clinical conditions which include idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, cystic fibrosis, emphysema, etc. Studies have shown a strong association of certain gene variants with impaired lung function. This book includes some of the vital pieces of work being conducted across the world, on various topics related to pulmonary diseases. It provides significant information of this discipline to help develop a good understanding of the role of genetics in the incidence of these disorders. Coherent flow of topics, student-friendly language and extensive use of examples make this book an invaluable source of knowledge.