Hi Rick,     Asthma is a clinical syndrome that may include cough, wheezing, shortness of breath or chest tightness. Some people only cough when their asthma is active. Asthma is caused by inflammation in the airways of the lung. Mucus secreting cells called mucus glands line the airways of the lung and over produce mucus when asthma is triggered by allergens, irritants or infection.   Complaints of cough and excessive phlegm (or mucus) are common during asthma attacks, especially if brought on by a cold or sinus infection. Asthma is not well controlled when bothersome cough frequently occurs. Usually an inhaled steroid is required to reduce inflammation and prevent asthma attacks.   There are other diseases that may cause cough and phlegm production in a non-smoker but they are not as common as asthma. The test you had is called "spirometry" which is a type of pulmonary function test. This test is used to confirm the diagnosis of asthma and to measure the degree of control and level of severity.   There is plenty more to learn about asthma on this website. If you have more questions please come back to post them.     Yours,   J. Thompson, MD