The effect of exercise on skin blood flow (SkBF) in exercising and non-exercising limbs is not well described. SkBF might differ between exercising and non-exercising limbs due to differences in local tissue temperature and/or vasoconstrictor tone. The aim of this study was to examine exercising and non-exercising limb SkBF responses to knee-extensor exercise in normothermic and heat stress conditions. Exercising thigh and non-exercising arm skin blood flow (laser-Doppler flowmetry), blood pressure (radial catheter), rectal temperature (T_CORE) and mean skin temperature (T_SK) were measured in 5 active males (23±4 yr), dressed in a tube-lined water-perfused suit, at rest and during 6-min of one-legged knee-extensor exercise (25±3 W) in 4 conditions; 1) control (mean ± S.D; T_CORE 37.0±0.2 °C, T_SK 32.3±0.3 °C), 2) skin hyperthermia (T_CORE 37.1±0.2 °C, T_SK 36.5±0.5 °C), 3) skin and mild core hyperthermia (T_CORE 37.9±0.2 °C, T_SK 37.1±0.6 °C) and 4) skin and high core hyperthermia (T_CORE 38.5±0.2 °C, T_SK 37.6±0.4 °C). Hydration status was maintained throughout. Data were analysed using a one-way repeated measures ANOVA. At rest, leg cutaneous vascular conductance (CVC) increased with T_SK hyperthermia and T_SK and mild T_CORE hyperthermia compared to control (0.48±0.07 and 0.62±0.16, respectively, vs 0.10±0.08 AU.mmHg^-1, P=0.001), but did not increase further with T_SK and high T_CORE hyperthermia (0.63±0.13 AU.mmHg^-1, P>0.05). Similarly, arm CVC increased with T_SK and T_SK and mild T_CORE hyperthermia (0.22±0.16 and 0.72±0.61 vs 0.07±0.02 AU.mmHg^-1, respectively, P=0.043) and thereafter plateaued (0.80±0.48 AU.mmHg^-1, P>0.05). In the transition from rest to exercise, leg CVC increased and the magnitude was significantly lower during each heat stress condition compared to control (278±148 vs 29±31, 34±41, 32±34 %, all P<0.05). Similarly, arm CVC increased with exercise and the magnitude of the increase was reduced during the last 2 heat stress stages (1; 74±51, 2; 160±147, 3; 11±15, 4; 2±7 %, P=0.031). The increase in CVC during control exercise was larger in the leg vs the arm (P=0.043) but there were no limb differences during heating (all P>0.05). Mean arterial blood pressure (MAP) was well maintained throughout heat stress (~100 mm Hg, P=0.19). During exercise, the MAP increase was progressively reduced with heating (35±16 to 10±7 mm Hg, P=0.012) in line with the reductions in exercise-induced CVC increases with increasing heat stress. These findings demonstrate that CVC increases during knee-extensor exercise in exercising and non-exercising limbs and that the magnitude of the increase is larger in the exercising limb under normothermic conditions, possibly through an increased tissue temperature. Furthermore, the size of elevation in CVC is reduced with increasing pre-exercise T_SK and T_CORE in exercising limbs but only with increasing T_CORE in non-exercising limbs.