Nicotinic acid effectively inhibited the posttraumatic increase in both free fatty acids (FFA) and fibrinolysis inhibition activity (FIA) in the blood in rats, indicating that FFA might be involved in the posttraumatic increase of FIA. The FIA in the liver was greater than that in other organs studied and was increased in the posttraumatic phase. The possible role of the liver in the posttraumatic increase of FIA is discussed.