We applied the standard treatment with streptokinase to 52 cases of deep venous thrombosis and 35 cases pulmonary embolism. Angiography demonstrated total lysis of the clot 22 times, partial lysis 42 times, and no lysis 23 times. The absence of lysis was more frequent in venous clots than in pulmonary clots. Early treatment was more effective, achieving complete lysis in 21 of 22 cases. Nevertheless, in deep venous thrombosis, late treatment can result in partial lysis and set an important venous junction free. With the standard treatment, the biologic controls showed good lysis in 75% of the cases, insufficient lysis in 15%, and no lysis in 10%. The extent of the thrombosis is an important point. The clot was totally lysed in 9 of 10 cases of localized deep venous thrombosis. In patients with pulmonary embolism, about 30% of the obstructed surface is cleared. Nevertheless, in such cases we must take into consideration not only the nonperfused pulmonary area, but also the venous starting point of the clot.