1.The purpose of this study was to determine if humid heat acclimation improves thermoregulatory function at the level of the eccrine sweat gland.2.Mean rectal temperature and heart rate were significantly (p<0.05) reduced by 0.5°C and 17bpm, respectively, during an 8-day heat acclimation protocol in 13 male subjects.3.Whole-body sweat rate was also significantly increased 20% during the same time period. The most important new finding was that humid heat acclimation produced a significant 63% increase in pilocarpine-induced sweat rate. These results strongly suggest that heat acclimation improves sweat gland function via a peripheral mechanism.