Acute systemic blood changes were measured in New Zealand white rabbits after severe and mild frostbite injury to the foot. There were observed after 72 hr, in the severely frostbitten rabbits, a decrease in erythrocytes, hematocrit, lymphocytes, and albumin, and an increase in total leukocytes, neutrophils, platelets, fibrinogen, and antithrombin III. Mildly frostbitten rabbits showed similar changes except for no changes in the platelets, albumin, and antithrombin III. In severely frostbitten rabbits, after 72 hr, the changes in the plasma coagulation tests were a prolonged partial thromboplastin time, an accelerated prothrombin time, and increased activities of Factors VII, IX, X, and XI. In mildly frostbitten rabbits there were a prolonged partial thromboplastin time and an increased activity of Factor VII. No changes in fibrinolysis were seen in either group of rabbits. Platelet aggregation, studied only in the severely frostbitten rabbits, showed a change only by an increase in the slope of the collagen-induced platelet aggregation. The blood changes observed in the rabbit model are different than those reported in human frostbite cases. No disseminated intravascular coagulation was apparent in the rabbit model after frostbite injury.