The objective of this research is to prepare human plasma plasminogen and plasmin, and the plasmin-derived light (B) chain together with their stoichiometric-streptokinase complexes, and human plasma alpha2-plasmin inhibitor, in quantities needed to study the behavior of plasminogen-derived activators in human subjects with thromboembolic diseases. The plasminogen-derived streptokinase complexes could have potential therapeutic use as thrombolytic agents. The alpha 2-plasmin inhibitor could have potential use in those patients undergoing thrombolytic therapy with excess bleeding. Specially-prepared clinical preparations of the activator complexes will be used to treat patients with deep-vein thrombosis, using single low-doses. The patients, in 3 groups, will be monitored for 24 hours by standard laboratory tests and new assay methodology on components of the fibrinolytic system, and after 48 hours by venography.