Neutrophils play a key role in the pathogenesis of CF lung disease. We know that neutrophilic inflammation is related to a decline in pulmonary function. Therefore, early anti-inflammatory intervention is an opportunity to slow this irreversible pulmonary destruction. However, the development of sensitive, non-invasive diagnostic tools of airways inflammation is essential to the study and implementation of anti-inflammatory therapies. Our current armentarium of measures of airways inflammation is limited. BAL is invasive and not clinically acceptable as a tool for the serial measurement of inflammation. Sputum samples are highly variable and not reliable.