Evidence is presented in rats that the liver is involved in clearance from the circulation of the coagulant intermediate, product I. Although product I injected into the general circulation failed to elicit the defibrination syndrome, similar injections accompanied by ligation of the hepatic blood supply were followed by a significant drop in plasma fibrinogen. Product I was largely inactivated following perfusion through the liver, but addition of antiheparin drugs to the perfusate prevented this inactivation. No anticoagulant activity could be demonstrated in perfused material. Perfusion through the liver of product I precursors demonstrated inactivation of factor IX but no effect on factors V, VII, VIII, or X. * This study was supported by Grant # HE-05415-02 of the National Heart Institute, National Institutes of Health, United States Public Health Service.