We report 2 patients who developed massive pulmonary embolism with greater than 50% occlusion of the pulmonary arterial circulation. Hypotension, syncope and right sided failure were the clinical manifestations. Immediately after diagnostic pulmonary arteriography, 20,000 U of streptokinase (SK) were delivered in the pulmonary artery next to the thrombotic mass. A continuous infusion of SK, 10,000 U/h was maintained for 24 h in one patient and 72 h in the other. Rapid clinical improvement was observed in the following 24 h. Control angiography showed lysis of the embolus with residual obstructions of segmentary branches. The clinical value of this form of treatment for pulmonary embolism is discussed.