We evaluated a technique for treating hypothermia that uses extracorporeal circulation but does not require heparin or pump assistance. Hypothermia to 29.5 degrees C was induced in eight anesthetized dogs, and thermistors placed in the pulmonary artery, liver, bladder, esophagus, rectum, muscle, and skin. Four experimental animals were rewarmed by creating a fistula which connected arterial and venous femoral lines to an interposed counter-current heat exchanger. External rewarming was used in four controls. Bleeding time (BT), coagulation profile (PT, PTT, TT), and cardiac output (CO) were measured during rewarming. Core temperature (T) rose significantly faster with CAVR (0.00001). Average time to rewarming was 45 min, vs. 4 hrs in controls. Haptoglobin, platelet, fibrinogen, and fibrin split product levels were unaffected. Continuous arteriovenous rewarming (CAVR) improved T, CO, BT, and coagulation profile faster than any method yet reported not requiring heparin or cardiac bypass. The application of CAVR in post-traumatic hypothermia warrants further investigation.