Chronic obstructive pulmonary disease (COPD) and asthma are associated with morphological changes in airway and lung and metalloproteinases are tought to play a role in this destruction. The aim of this study is to compare the levels of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinases (TIMP)-1 in the airways of COPD and asthma patients in stable period. We measured MMP-9 and TIMP-1 levels in the induced sputum of 20 asthma, 22 COPD patients in stable period and 15 healthy controls. MMP-9 and TIMP-1 levels were measured by using ELISA kits. MMP-9 and TIMP-1 levels were higher in patient groups than the controls. In COPD patients MMP-9 and TIMP-1 were significantly higher than the controls (respectively; p= 0.0001, p= 0.0001). Similarly, in asthma patients MMP-9 and TIMP-1 levels were higher than the controls (respectively; p= 0.005, p= 0.002). However, while there were no significant difference in MMP-9 levels between the patient groups (p= 0.29), TIMP-1 levels were significantly higher in COPD patients (96.2 +/- 58.2 versus 52.8 +/- 52 microg/mg protein, respectively, p= 0.0001). Atopic asthma patients TIMP-1 levels were slightly higher than non-atopic asthma patients (p> 0.05). There was no significant correlation between FEV(1) and MMP-9 or TIMP-1 levels in all groups. Although known pathogenetic differences in COPD and asthma, the increases in protease-antiprotease levels in both two patient groups may be associated with bronchial and parenchimal morphological changes. New treatment strategies which are focused on modulating of increased protease-antiprotease levels may be give a hope to patients with COPD and asthma.