As far as therapy is concerned, atherosclerotic arteriopathy may be divided into acute and chronic forms. In acute embolic forms, therapy should be surgical. Only in cases of peripheral embolism or polyembolism, and in rare cases for which vascular surgery cannot be adopted, can thrombolysis be carried out with UK. In acute thrombotic forms, therapy should be medical, because a thrombus of recent formation is rich in fibrin and may be lyzed by UK. Total recanalization takes place in 61% of cases treated, partial recanalization in 23%. Subsequently perviousness is maintained by adequate antithrombotic therapy. In chronic arteriopathy, the thrombus is lacking or almost lacking in fibrin and thrombolytic therapy is not indicated. Special therapeutic combinations are used containing platelet inhibitors (ticlopidine), antifibrin drugs (subcutaneous heparin), minor fibrinolytic agents (mesoglycan) and hemorheological drugs (pentoxyphylline). This therapy seems to give good results, as showed by the low percentage in amputation calculated on 2,565 patients treated and kept under observation for 5 years. Finally let us consider chronic progressive arteriopathy. This term indicates a very advanced stage, characterized by a gradual irreversible change for the worse leading towards gangrene. As a last resort, before amputating, a thrombolytic therapy with UK was tried to see if with strong fibrinolysis continued for 3 days amputation might be avoided. In a pilot study carried out on 12 patients, the angiographic data showed only partial lysis in small arteries or arterial branches. Clinical data showed reduction or disappearance of pain at rest in 80% of cases. In 70% of cases gangrene disappeared if it was initial and superficial, it was delimited if already in progress.