Extra-cellular neutrophil collagenase and elastase were demonstrated by immunochemical methods in crevicular material from clinically healthy and chronically inflamed human gingivae. Collagenolytic activity was shown by viscosimetry and elastolysis by its digestive action on elastin agarose plates. Also the serum protease inhibitors,a,1-antitrypsin anda2-macroglobulin, were demonstrated in the crevicular material. The inflamed gingivae contained increased amounts of enzymes and inhibitors. The protease inhibiting capacity ofa1-antitrypsin was saturated in material from inflamed as well as from healthy gingivae, but free neutrophil collagenase and elastase were found mainly in crevices of the inflamed gingivae. It was suggested that free activities of these two proteolytic enzymes might contribute to collagen break-down in gingivitis and periodontitis.