Surgical preparation of a lung lymph fistula in sheep was previously shown to induce temporary permeability disturbance of pulmonary microvessels. Flow and composition of lung lymph were compared in 19 sheep with acute, and 16 with chronic lymph fistula. Lymph and plasma were analyzed regarding activities of prothrombin, antithrombin III, prekallikrein, kallikrein, functional kallikrein inhibitors and 11 acid hydrolases of lysosomal origin. Levels of prothrombin and antithrombin III fell postoperatively in plasma and reached even lower values in lymph, indicating systemic activation of the coagulation system as well as local activation in the lung. The studied components of the plasma-kallikrein system were unchanged. Lysosomal enzymes were released in lung lymph, reflecting cell injury in the lung. Local activation of proteolytic enzyme systems thus occurs in the lung after trauma. Analysis of organ-specific lymph (= interstitial fluid) may contribute to better understanding of the pathophysiology of trauma.