Acute pleural empyema which is not amenable to pleural puncture or closed thoracic drainage should be treated operatively by decortication or, in persistent cavities, by open thoracostomy drainage. In the last 2 years we have instilled 500,000 IU of fibrinolysines (streptokinase and streptodornase) per day into the pleural cavity of 27 patients with pleural infections requiring closed intrapleural drainage. By means of this treatment, pus and fibrinous membranes are liquefied and necrotic tissue is discharge. Therapeutic success is indicated by considerably increased fluid drainage about one hour after instillation. This therapy was performed for an average of 5 days. In 12 patients (44%) pleural empyema could be cured. In the other 15 cases decortication, and in 3 of them open thoracostomy drainage, was necessary. In our opinion intrapleural instillation of fibrinolytic enzymes should be added to the well-recognized method of treatment of pleural empyema, although not replace them.