When cell counts are performed on weighed sputum selected from the saliva, treated with dithiothreitol, and filtered to obtain a homogeneous suspension of cells, they provide a total and differential cell count, as well as a semiquantitative measure of free eosinophil granules and macrophage smokers inclusions. The cell counts have good test qualities, have known normal values (with mean and median values for eosinophils of 0%), and identify the presence, severity, and type of inflammation. Three types of cellular inflammation are recognized (eosinophilic, neutrophilic, or both), and there are several known environmental causes of these inflammations. For example, eosinophilic bronchitis (usually indicated by an increase in the percentage of eosinophils and a total cell count that remains in the normal range) can result from hypersensitivity to inhaled allergens or occupational chemical sensitizers as well as from unknown causes. The causes of neutrophilic bronchitis include cigarette smoke or atmospheric pollutants, which usually increase the percentage of neutrophils, or confirmed viral8,9 or suspected bacterial10 infections, which also increase the total cell count and are, therefore, more intense.