Intraoperative hypothermia is difficult to avoid and may present a significant clinical risk during the early postoperative phase. We evaluated a forced-air system [Bair Hugger, OR-type (BH)] for warming intraoperative patients with open abdominal surgery. Twenty patients received BH warming [BH(+) group] and another 20 patients, who served as controls, did not [BH(-) group]. Patients in both groups also received circulating blanket warming. Tempertures were measured at 30-min intervals throughout the operation in the rectum and on the tip of the index finger opposite the nail bed. The average operation time was 168.8±16.2 min. Rectal and fingertip temperatures in the BH(+) group were significantly higher than those in the BH(-) group, and central-peripheral temperature gradients in the BH(+) group were significantly smaller than those in the BH(-) group during the study, except at 180 min. No shivering occurred in either group. Therefore, BH is an effective warming device during open abdominal surgery.