Introduction: Although 15% of the total race duration in cycling or triathlon can be performed at intensities beyond VO2max, little is known about the effectiveness of dietary NO3- supplementation on tolerance to supramaximal intensity intermittent exercise in endurance athletes. Our aim was therefore to determine whether dietary NO3- supplementation enhances the tolerance to supramaximal intensity intermittent exercise in elite endurance-trained athletes. Methods: Using a randomized, single-blind, cross-over design, 9 elite endurance athletes 3.7 years, maximal oxygen uptake performed a supramaximal intensity intermittent exercise test following either a 3-day beetroot juice supplementation (BJ, NO3- content of 680 mg L−1), or a placebo supplementation (PL, NO3- content <5 mg L−1). The exercise test consisted of 15-s cycling exercise bouts at 170% of the maximal aerobic power interspersed with 30-s passive recovery periods performed until volitional exhaustion. Gas exchange measurements (indirect calorimetry), changes in local muscle oxygenation, and microvascular THb concentration were measured by Near Infrared Spectroscopy (NIRS). Results: Dietary NO3- supplementation did not increase the tolerance to supramaximal intensity intermittent exercise (). Dietary NO3- supplementation did not affect oxygen uptake (VO2) during supramaximal intensity intermittent exercise tests . The area under the curve for microvascular total hemoglobin (AUC-THb) was not different between the two conditions Discussion/conclusion: A short-term dietary NO3- supplementation did not increase the tolerance to supramaximal intensity intermittent exercise in elite endurance athletes high VO2max (>60 mL kg−1 min−1).