There has been no reported effect of acute or chronic dietary nitrate supplementation on exercise in the heat, despite thermal balance depending upon a number of modifiable factors, many of which could be altered by the physiological effects elicited by the nitrate-nitrite-nitric oxide pathway (NO– NO-—NO) (Amano et al., 2018; Kent et al., 2018). However, these studies have not been conducted in hot, dry environments, during exercise of higher intensities, which might provide the necessary conditions to realise these effects. Furthermore, based on previous reports (Porcelli et al. 2015), it is feasible that the potential effects of dietary NO-are potentiated among participants of lower training status, who might also have greater capacity for acute heat adaptation. The aim of this study was to determine the effect of 5-days dietary nitrate consumption on exercise tolerance, thermoregulation and perceptual response during cycling in hot, dry conditions. Using a randomised, double-blind, crossover-design, 11 untrained participants (age: 23 ± 7 y; stature: 182.0 ± 5.2 cm; body mass: 78.7 ± 7.5 kg; VO2max: 48 ± 12 ml/kg/min) performed two trials to their limit of tolerance (Tlim) at the power output associated with their thermoneutral gas exchange threshold in a hot, dry (35 °C & 30% relative humidity) environment, following ingestion of either 140 ml NO-in the form of a beetroot juice beverage ~9.2 mmol (BR) or placebo (PLA), for 5 days. Breath-by-breath gas analysis was performed, alongside continuous measurements of local sweat rates, heart rate (HR), rectal (Tc) and weighted mean skin temperatures (Tskin). Thermal sensation and rating of perceived exertion (RPE) were also measured. Nude body mass was recorded pre- and post-exercise as an indication of whole-body sweat rate. Plasma [NO-] was increased in BR vs.PLA (P< 0.001) following the 5-day supplementation. There were no changes in Tlimbetween conditions (PLA: 21.6 ± 7.4 min vs.BR: 23.1 ± 8.3 min; P= 0.171) and there were no main effects of condition for Tc(PLA: 37.5 ± 0.04 °C vs.BR: 37.4 ± 0.13 °C; P= 0.629), Tskin(PLA: 35.4 ± 0.17 °C vs.BR: 35.5 ± 0.16 °C; P= 0.763), HR (PLA: 169 ± 4 beats/min vs.BR: 171 ± 3 beats/min; P= 0.685), or sum of local sweat rates (PLA: 557 ± 38 nL/min vs.BR: 565 ± 41 nL/min; P= 0.832). The RPE (PLA: 16.2 ± 0.3 vs.BR: 16.1 ± 0.4; P= 0.635) and thermal sensation (PLA: 2.8 ± 0.2 vs.BR: 2.8 ± 0.2; P= 0.858) were also not affected by condition. There were no interactions between time and condition across all variables (P< 0.05). Despite a 1.0 ± 0.5 % loss of fluid in the NO-condition vs.PLA (0.7 ± 0.2 %), there were no significant differences (P= 0.170). Five-days of NO-supplementation had no effect on Tlimin dry heat, nor did it alter thermoregulation or perceptual responses of untrained participants.