Asthma is a disease that affects the lungs. It causes repeated episodes of wheezing, breathlessness, chest tightness, and night-time or early morning coughing. Tens of millions of people throughout the world suffer from asthma. Airways are the paths that carry air to the lungs. As the air moves through the lungs, the airways become smaller, like branches of a tree. During an attack, the sides of the airways in the lungs become inflamed and swollen. Muscles around the airways tighten, and less air passes in and out of the lungs. Excess mucus forms in the airways, clogging them even more. The attack, also called an episode, can include coughing, chest tightness, wheezing, and trouble breathing. Environmental exposures, such as house dust mites and environmental tobacco smoke, are important triggers of an attack. This new book presents important new research on the causes on asthma as well as its diagnosis and treatment.