Thirteen patients with up to two-week-old phlebothromboses were treated with streptokinase and human plasminogen according to a fixed dosage scheme. In six cases reopening of the vein was complete, in three cases partially complete. In four cases thrombolysis had to be stopped due to macrohaematuria. Haemorrhagic complications occurred mainly after the third day of treatment. Substitution of human plasminogen during continuous streptokinase administration is, in the case of demonstrable lowering of the plasma plasminogen level, a valuable addition to the thrombolytic concept.