The core temperature triggering thermoregulatory arteriovenous shunt constriction is defined as the threshold for vasoconstriction. Vasoconstriction helps prevent further core hypothermia by decreasing cutaneous heat loss and constraining metabolic heat to the core thermal compartment. A previous study showed isoflurane inhibited thermoregulatory threshold. However there is no study to confirm whether sevoflurane perturb thermoregulatory vasoconstriction or not. Consequently we tested the hypothesis that 1.0 minimum alveolar concentration (MAC) sevoflurane and 1.0 MAC isoflurane would reduce the vasoconstriction threshold comparably. With institutional review board approval, we studied 20 patients, aged 20-60 yr, undergoing open abdominal surgery. No premedication was given. Ten patients each were anesthetized with 1.0 MAC sevoflurane (2.0%) alone or 1.0 MAC isoflurane (1.2%) alone. A forearm minus fingertip, skin temperature gradient 0 degree C was considered to demonstrate significant vasoconstriction; the esophageal temperature triggering vasoconstriction identified the threshold. Morphometric characteristics were comparable in each group. The threshold for vasoconstriction was 35.1 +/- 0.4 degrees C in the patients given 1.0 MAC sevoflurane, which was comparable that in those given 1.0 MAC isoflurane: 35.3 +/- 0.7 degrees C. We thus conclude that sevoflurane impairs thermoregulation comparably with isoflurane.