The effect of fivrinolytic enzyme produced from Bacillus subtilis K-54 on the thrombosis and stress in vivo was investigated. Each partially purified fibrinolytic enzyme of 4 protein casein unit was administered orally for 3 days before intravenously injection with collagen and epinephrine. In the mice group administered with the enzyme and increased life span of mice was observed in comparison with that of control. The result suggest that the enzyme may prevent the formation of thrombos in vivo. Administration of the enzyme did not influence to stress itself because 5-hydroxyindoleacetatic acid concentration of brain in the mice group with stress did not decreased after the administration of the enzyme. The value of lipid peroxide (LPO) of the liver and brain cells in the group treted with the enzyme was lower than that of control. However, protein degradation (PDP value showed no significant difference between treatment and control groups. In addition, the value of activated partial thromboplastin time (APTT), protrombin time (PT0 and antiplasmin in blood were higher in the stress group than that of the enzyme treated group.