Sputum was collected from patients with purulent chronic bronchitis. Immuno-chemical techniques using rabbit antiserum against human granulocyte collagenase and elastase showed the presence of both enzymes. Also the serum protease ingibitors alpha1-antitrypsin and alpha2-macroglobulin were demonstrated. Their protease inhibiting capacity was saturated. Granulocyte elastase and collagenase occurred not only in complexes with the inhibitors, but also as free enzymes. All sputa showed free proteolytic, elastolytic and collagenolytic activity. The concentration of collagenase was equal in the sol phase and in the gel phase of the sputa, but most of the elastase was bound to the gel phase.