Bovine plasma yields fibrinolytically inactive euglobulin fractions, even when prepared in the presence of dextran sulphate. Addition of flufenamate to these solutions only occasionally elicits a slight activity. However, highly fibrinolytic solutions are produced when euglobulins precipitated in the presence of dextran sulphate are exposed to chloroform. Evidence indicates that a plasminogen activator is formed, which subsequently converts plasminogen present in the fractions to plasmin. Bovine euglobulin fractions contain an inhibitor which seems to be specifically directed towards urokinase and not to plasmin or to tissue plasminogen activator. Its inhibiting capacity is decreased after treatment with chloroform.