Individuals with cystic fibrosis (CF) have persistent infection in the airways, which the body attempts to fight by recruiting immune cells (neutrophils) to the lung. The immune system and neutrophils are unable to completely kill the bacteria, and the response to the infection leads to inflammation (swelling) of the airways and lung damage. Nitric oxide (NO) has anti-bacterial and anti-inflammatory properties in the lung. NO production is decreased in CF patients, and may contribute to the persistent infection and inflammation. Increasing the production of NO in the airways of CF patients may help decrease this inflammation and infection.