In this study, we analysed the cellular component of induced sputum in healthy control subjects (n = 30), asthmatics (n = 44), patients suffering from COPD (n = 15), pulmonary tuberculosis (PTB) (n = 14) and healthy steel workers (HSW) (n = 14). Sputum was induced by inhalation of hypertonic saline (NaCl 5%) for 20 min. When compared to the healthy control group, all the disease groups as well as the one of healthy steelworkers exhibited significantly higher total sputum cell counts. Analysis of the differential cell counts showed that there was a significant increase in % eosinophils in asthmatics, in % neutrophils in COPD, asthmatics, tuberculosis and healthy steelworkers and in % lymphocytes in pulmonary tuberculosis. Our study illustrates the feasibility and the possible clinical application of induced sputum analysis in several pulmonary diseases and shows how this technique could be useful in assessing airway inflammatory processes in subjects exposed to industrial pollutants.