SummaryRecent deep vein thrombosis of the iliofemoral segment often leads to pulmonary embolism and to impaired valve function. Although more common, occlusions in the calf veins are less dangerous, and often a self-limiting disorder as almost half of these thrombi lyse spontaneously. Approximately 70 % of fresh deep venous thrombi dissolve under intensive and prolonged thrombolytic treatment with streptokinase and long term follow-up study indicate that normal valve function is preserved in those patients in whom thrombus clearance was obtained.Thrombolysis with streptokinase or urokinase appears to be the current treatment of choice for most cases of massive and severe, lifethreatening pulmonary embolism; those patients surviving more than an hour or so after massive infarction comprise a prognostically better group, for whom the chances of surviving embolectomy is actually smaller than the probability of survival without surgery but with thrombolytic treatment.Several large scale trials with streptokinase and one with urokinase in patients with recent myocardial infarction have been performed. In general, trials conducted in coronary care units have shown no significant increase of the survival rate but the mortality in the control group was low, while studies conducted in general wards had a higher mortality in the control group, which in most studies could be significantly reduced by thrombolytic therapy. The results of other trials have been completed but not yet reported; it is hoped that these studies will help in defining the position of thrombolytic therapy in the treatment of myocardial infarction.Acute peripheral arterial thromboembolism was the first clinical situation for which serial angiographic studies established beyond doubt that thrombolytic agents are indeed capable of dissolving spontaneous thrombi and emboli inman. Since then, major progress in vascular surgery (Fogarty balloon catheter) has been made and this approach is now to be preferred, if feasible.In chronic arterial insufficiency, complete arterial occlusions and stenotic lesions have also been removed by thrombolytic treatment. This treatment is probably best reserved for patients with severe symptoms not requiring rapid relief, with a relatively poor operative prognosis and with short occlusions (less than 12 cm), inducing clinical symptoms since less than 12 months.