The bleeding tendency in acute chloroform intoxication is due to deficiency in both plasma fibrinogen and plasma prothrombin. If the disorder is mild, no bleeding occurs. However, the prothrombin falls to rather low levels, although the fibrinogen falls only moderately. A bleeding tendency may also be produced by giving small repeated doses of chloroform. In such experiments, the hemorrhagic tendency is due to a deficiency in prothrombin alone. The fibrinogen level is unaffected. The relation of the liver injury to the plasma prothrombin level indicates that the liver is concerned in the manufacture of prothrombin. Prothrombin formation appears to be more easily interfered with than does fibrinogen formation.