The vascular tree of the legs of human corpses was perfused with 0.15 M NaCl, and eluted with 2 M KSCN and finally with 0.15 M NaCl. The average total activity of human vascular plasminogen activator and protein eluted per leg was 29 800 Ploug units and 8.3 g respectively. Fibrin-Sepharose adsorbed the plasminogen activator activity, which could be eluted with 2 M KSCN. A small column containing from 0.5--1.9 ml of phenyl-Sepharose, normally coupled directly to the outlet of the fibrin-Sepharose column, adsorbed all the plasminogen activator activity. Elution of this hydrophobic matrix yielded a plasminogen activator preparation 17% pure judging from sodium dodecyl sulphate polyacrylamide gel electrophoresis. By this method human vascular plasminogen activator was found to have an Mr of 60 000. Upon reduction, two bands of Mr 30 000 and 31 000 were estimated. Human vascular plasminogen activator could be inhibited by diisopropylfluorophosphate. Isoelectric focusing yielded four major bands with the isoelectric points of 6.9, 7.4, 8.0 and 8.6. Human vascular plasminogen activator was found to be a relatively stable protein in purified form.