Sputum will be obtained with hypertonic saline by the method described by Pizzichini et al(14) inhaling increasing concentrations of saline (3, 4 and 5%) each for 7 minutes, through a mouthpiece. After each period of inhalation, FEV1 will be measured for safety. Subjects will be asked to cough sputum into a sterile container. Total cell count of leukocytes will be obtained in a modified Neubauer haemocytometer. The cell viability will be determined by the trypan blue exclusion method. Four hundred non squamous cells will be counted in Wright-stained slides and the results will be expressed as a percentage and absolute number of the total non squamous count. Measurement of MMP-9, 12 TIMP-1 and TGFb will be performed in sputum supernatant.