The thermoregulatory responses to exercise heat stress under hypoxic conditions are unclear due to variations in methods of prescribing exercise workloads in both sea-level and hypoxic conditions (Kacin et al., 2007) and in the measurement of cutaneous vascular responses (Kolka et al., 1987; Miyagawa et al., 2011). The aim of this study was to examine the thermoregulatory responses to exercise at a fixed metabolic heat production (Cramer & Jay, 2014) in combined heat and hypoxia stress. Eight healthy, unacclimatised males (23.5 ± 2.5 yr, 77 ± 10.23 kg, 1.81 ± 0.08 m, sea-level VO2peak 3.5±0.5 L.min-1 and hypoxia VO2peak 2.8±0.4 L.min-1) underwent 40 minutes of steady state cycling at a fixed metabolic heat production (592±33 Watts, 7.7±0.7 Watts.Kg-1, VO2; 2.1 ±0.1 L.min-1, Power Output; 144±18 Watts) at 28 °C (40% relative humidity) under 2 different inspired fractions of oxygen; 1) Sea-level and 2) Hypoxia (13 % FIO2). Local skin blood flow (SkBF; laser Doppler flowmetry; expressed as cutaneous vascular conductance; CVC) and local sweat rate (SR; capacitance hygrometry) on the forearm and whole-body SR were recorded. Core (TCORE; intestinal pill) and local skin temperatures (TSK), blood pressure (BP; automated sphygmomanometry and digital photoplethysmography), heart rate (HR; ECG) oxygen saturation (SpO2; pulse oximetry) were also monitored. Mean body temperature (TBODY; product of TCORE and TSK) thresholds for heat stress-induced elevations in SkBF and SR, as well as the SkBF/SR:TBODY slopes were calculated. Data are presented as Means±1SD. During exercise in Hypoxia SpO2 was lower (97±1 vs. 81±5 %, P<0.001) and HR was higher (129±23 vs. 148±27 beats.min-1, P<0.001). both TCORE (37.5±0.4 vs 37.7±0.4 °C, P<0.01) and TSK (33.6±1.0 vs 34.4±0.7 °C, P<0.01) were higher in Hypoxia. Whole-body SR was higher during exercise in Hypoxia (0.87±0.49 vs. 1.38±0.87 L.hr-1.ΔTBODY °C, P=0.07). During exercise the forearm SR TBODY threshold (36.7±0.2 vs. 36.8±0.2 °C, P=0.18) was not different between trials whereas the forearm SR:TBODY slope (1.7±1.0 vs. 2.1±1.0 mg.cm2●min-1●°C, P=0.03) was increased during Hypoxia. The forearm SkBF TBODY threshold (36.7±0.3 vs. 36.9±0.1 °C, P=0.22) was not different between trials nor was the forearm SkBF:TBODY slope affected during Hypoxia (63±47 vs. 110±65 CVC %Maximum units●°C, P=0.23). Thermal discomfort (6±1 vs. 7±1 units, P<0.01) and ratings of perceived exertion (13±1 vs. 14±2, P<0.01) were higher during exercise in Hypoxia. During exercise-heat stress performed at a fixed metabolic heat production under hypoxic conditions core temperature and thermal discomfort are increased relative to sea-level. These findings do not appear to be caused by impaired vasodilatory and sweating thresholds or local vasodilatory sensitivity, rather, whole-body and local sweating sensitivity are increased during hypoxia; possibly via a higher skin temperature.