The purpose of this study was to assess the ability of patients with burns on 30 to 40% and 60% or greater of their BSA to thermoregulate their core temperature during exercise in the heat. Two groups (n = 3 in each) of subjects with healed third-degree burns (34.0 +/- 1.4% and 77.7 +/- 12.4%, respectively) and a group of unburned subjects (n = 2) exercised for 1 hour on a cycle ergometer at 75 Watts in an environmental chamber set at 35degreesC and 60% relative humidity. Subjects were monitored for rectal and skin temperatures, heart rate, whole body sweat rate, skin blood flow, and active sweat gland density (number per cm(2)) in unburned, burned, and harvested skin. The results demonstrated that patients with burns on 60% or greater BSA did not show an intolerance to moderate exercise in the heat, as evidenced by only a moderate rise in rectal temperature and heart rate. Furthermore, the responses were similar to those of the unburned subjects.