SummaryMiscellaneous pharmacological agents have been claimed to enhance fibrinolysis by liberation of endogenous activators but most of them, especially the vasoactive drugs, have only a transient effect.After administration of phenformin (100 mg/d) plus ethyloestrenol (8 mg/d), the plasminogen activator activity in vein walls (biopsy specimens from superficial hand veins) increased in healthy volunteers, but the fibrinolytic response to venous occlusion did not change.In patients with thrombotic disease, before treatment with this combination, abnormally low plasminogen activator content in the vein walls and/or low fibrinolytic activity on venous occlusions was observed in all cases. After treatment, the plasminogen activator level in the vein wall increased significantly and the release in response to venous occlusion increased to normal levels in most of the patients, indicating both a stimulation of the synthesis and the release of plasminogen activator. It took at least three months treatment to obtain normal level and response.The anabolic steroid ethyloestrenol alone has a similar effect after three months, but the response to venous occlusion was not so striking, and no further increase was found during the treatment.With moroxydine chloride, a phenformin-like substance, the plasminogen activator activity of the vessel wall was normalized in most of the patients, but the increased release capacity was not stable.A combination of an anabolic steroid and a biguanide thus seem to have the best stimulating effect on the endogenous fibrinolysis.