Hypothermia (Tcore max); the Mann-Whitney U test was used to test for significance of group differences. RESULTS. All groups were comparable for body weight, height, age, and amount of postoperative infusions. Temperatures at admission were 35.2 (33.435.9), 34.7 (34.335.8), and 35.4 (34.335.9) degrees C for groups R, B, and K, respectively. No significant differences in the rate of central rewarming could be found for these groups with 0.81 (0.411.32), 0.76 (0.401.07), and 0.70 (0.371.13) degrees C/h (Fig. 1). The mean VO2 of 3.41 (3.073.73), 3.55 (2.784.06), and 3.79 (2.517.00) ml/kg/min also did not differ significantly (Fig. 3). Significant differences between groups R and B [4.39 (3.746.19) and 4.30 (3.466.67) ml/kg/min] and K [5.92 (3.7910.64) ml/kg/min] were found for VO2 maxima during the course of investigation (Fig. 4). The heat balance revealed significant differences among treatment and control groups with -88 (-226+30), -41 (-212+12), and -191 (-265-86) kJ/h for groups R, B, and K. We additionally calculated the heat balance as a quotient, which showed 0.70 (0.221.07), 0.86 (0.441.04), and 0.49 (0.310.79) for groups R, B, and K (Fig. 4). The mean rate-pressure product of all groups did not differ significantly during the period of investigation. CONCLUSIONS. Neither external heat supply by radiant heat nor by a forced warm air system significantly reduced rewarming time in extubated, awake patients. As measured by heat balance, both active treatments saved about 20% more body heat production than in the control group. Continuing peripheral vasoconstriction may be the reason for the low efficiency of heat transfer. Thermal treatment did reduce the peak load (max. VO2) on the oxygen transport systems, though shivering was treated by pethidine if it occurred. External rewarming did not reduce the average load (mean VO2). Thus, concerning the goal of accelerating rewarming, it appears more rational to prevent intraoperative heat loss. For a comparison of efficiency of different warming devices, postoperative extubated patients do not appear to be an ideal model for study.