The purpose of this study was to investigate the effect of age on the capacity to acclimatise to exercise-heat stress. This study hypothesised that age would not affect body temperature and heat loss effector responses to short-term exercise-heat acclimation in trained subjects.Seven young subjects (19–32 years) were matched with 7 older subjects (50–63 years). Subjects were highly trained but not specifically heat acclimated when they exercised for 60min at 70%VO 2max in hot-dry (35°C, 40%RH) and thermoneutral (20°C, 40%RH) conditions, pre and post 6 days of exercise-heat acclimation (70%VO 2max , 35°C, 40%RH).Rectal temperature (T r ), skin temperature (T sk ), heart rate (HR), cutaneous vascular conductance (CVC) and whole body sweat loss (M sw ) were measured during each testing session and T r and HR were measured during each acclimation session.T r , T sk , %HR max , CVC and M sw were similar across age groups both pre and post heat acclimation. Following heat acclimation relative decreases and increases in T r and M sw , respectively, were similar in both subject groups. There was a significant reduction in heart rate (%HR max ) and increase in final CVC following the acclimation programme in the young group (all p<0.05) but not the older group.When comparing young and older well trained adults we found age affected the cardiovascular adaptation but not body temperature or whole body sweat loss to exercise-heat acclimation. These data suggest age does not affect the capacity to acclimatise to exercise-heat stress in highly trained adults undergoing short-term heat acclimation.