The efficacy of leg skin warming in preventing hypothermia and shivering was evaluated in two separate prospective, randomized trials in patients undergoing abdominal surgery. In the first trial, 22 patients were randomized to receive no hypothermia prevention (control group) or active warming with an electric warming blanket (electric blanket group). In the second trial 33 patients were randomized to receive no hypothermia prevention (control group) or forced-air warming (Bair Hugger® group) or forced-air warming with insulation of the air blanket from the environment (insulated Bair Hugger® group). The core and skin temperatures were measured and changes in body heat content calculated. In the first trial, core temperature was 34.6 ± 0.3°C at the end of surgery in the control group vs 36.4 ± 0.1°C in the electric warming blanket group (P < 0.001). Shivering occurred in nine control patients and in one warmed patient (P < 0.05). In the second trial, core temperature was 35.1 ± 0.2°C at the end of surgery in the control group, 36.3 ± 0.1°C in the Bair Hugger® group (P < 0.01) and 37.1 ± 0.1°C in the insulated Bair Hugger® group (P < 0.01 versus control; P < 0.05 versus Bair Hugger®). Shivering occurred in one patient of each warmed group and in seven of the control group (P < 0.05). Skin-surface warming limited to the legs provides sufficient heat (ranging 34 to 43 watts) to counterbalance heat losses during abdominal surgery.