By application of the correlation flow resistance/intrathoracic gas volume the lung emphysema is differentiated in quality within the scope of chronic obstructive lung diseases. For these groups immunoglobulins, the alpha1-trypsin activity in serum and the activity of further protease inhibitors were determined. There are no substantial variables in the different groups with regard to immunoglobulins. In the emphysema group alpha1-antitrypsin was a little reduced. This group included 2 patients with an alpha1-antitrypsin deficit. The two-dimensional separation of the inter-alpha-trypsin big inhibitor shows 3 areas which decrease significantly in case of severe emphysemata. The irritation of the inter-alpha-trypsin big inhibitor, i.e. in its turnover, parallel to the increasing degree of emphysema formation, is discussed.