Streptokinase therapy for the treatment of massive pulmonary embolism is superior to heparin therapy, although infusion of the recommended doses through a peripheral vein carries a substantial risk of hemorrhagic complications. By infusing low doses of this fibrinolytic agent through a pulmonary catheter in proximity to the embolic obstruction, rapid resolution of the pulmonary embolism can be accomplished. The induction of a local fibrinolytic state carries less risk of hemorrhagic complications than conventional streptokinase therapy. Further clinical studies are needed; however, this method of treatment of potentially fatal massive pulmonary embolism offers an attractive alternate to utilization of a fibrinolytic agent through a peripheral vein. The reduced risk of hemorrhagic complications could broaden its indications for therapy for pulmonary embolism to include situations in which embolic pulmonary obstruction has a high incidence of occurrence, that is, the postoperative state or the post-traumatic state.