Hypothermia occurs due to body heat redistribution between core and peripheral tissues as well as imbalance between heat loss and production. Perioperative hypothermia not only induces offensive shivering and prolongation of anesthetic recovery but also increases blood loss and incidence of surgical wound infection, increasing postoperative morbidity. It has been shown that intraoperative intravenous fluid administration and blood product transfusion have considerable effects on body temperature. Thus, it is important to monitor and control the temperature of fluids. Anesthesiologists should have knowledge of the characteristics of the various kinds of fluid warmer currently available and use them appropriately according to surgical procedures and the patient's position. It was reported recently that administration of amino acid can prevent intraoperative hypothermia, possibly by increasing the heat production in the body.