Therapeutic and prophylactic measures against a fibrinolysis following massive transfusion of preserved blood was studied, and following results were obtained. 1. Administration of ε-aminocaplonic acid, ACTH, and cortisone prevented a fibrinolysis following massive transfusion of preserved blood. 2. These therapeutics, especially, showed a marked preventive effect when they were applied together at early stage. 3. At the same time in the cases administed together with thromboplastin and adrenochrome preparations of every kinds as well as fresh blood, fibrinolysis was not completely prevented, but those were expected to inhibit other disturbance in coagulation mechanism accompanied with the above phenomenon.