This project tested the hypothesis that burn survivors can perform mild/moderate-intensity exercise in temperate and hot environments without excessive elevations in core body temperature. Burn survivors with low (23±5%TBSA; N=11), moderate (40±5%TBSA; N=9), and high (60±8%TBSA; N=9) burn injuries performed 60 minutes of cycle ergometry exercise (72±15 watts) in a 25°C and 23% relative humidity environment (i.e., temperate) and in a 40°C and 21% relative humidity environment (i.e., hot). Absolute gastrointestinal temperatures (TGI) and changes in TGI (ΔTGI) were obtained. Participants with an absolute TGI of >38.5°C and/or a ΔTGI of >1.5°C were categorized as being at risk for hyperthermia. For the temperate environment, exercise increased ΔTGI in all groups (Low: 0.72±0.21°C; Moderate: 0.42±0.22°C; High: 0.77±0.25°C, all P<0.01 from pre-exercise baselines), resulting in similar absolute end-exercise TGI values (P=0.19). Importantly, no participant was categorized as being at risk for hyperthermia, based upon the aforementioned criteria. For the hot environment, ΔTGI at the end of the exercise bout was greater for the High group when compared to the Low group (P=0.049). Notably, 33% of the Moderate cohort and 56% of the High cohort reached or exceeded a core temperature of 38.5°C, while none in the Low cohort exceeded this threshold. These data suggest that individuals with a substantial %TBSA burned can perform mild/moderate intensity exercise for 60 minutes in temperate environmental conditions without risk of excessive elevations in TGI. Conversely, the risk of excessive elevations in TGI during mild/moderate intensity exercise in a hot environment increases with the %TBSA burned.