The purpose of this study was to assess the reliability of a pre-loaded 1 500-m treadmill time trial, conducted in moderate normobaric hypoxia. 8 trained runners/triathletes (24 ± 3 years, 73.2 ± 8.1 kg, 182.5 ± 6.5 cm, altitude specific ...O2max: 52.9 ± 5.5 ml ⋅ kg-1 ⋅ min-1) completed 3 trials (the first as a familiarisation), involving 2, 15-min running bouts at 45 % and 65 % ... O2max, respectively, and a 1 500-m time trial in moderate normobaric hypoxia equivalent to a simulated altitude of 2 500 m (FiO2~15 %). Heart rate, arterial oxygen saturation, skeletal muscle and cerebral tissue oxygenation (StO2), expired gas (...O2 and ...CO2), and ratings of perceived exertion were monitored. Running performance (Trial 1: 352.7 ± 40; Trial 2: 353.9 ± 38.2 s) demonstrated a low CV (0.9 %) and high ICC (1). All physiological variables demonstrated a global CV ≤ 4.2 %, and ICC ≥ 0.87, with the exception of muscle (CV 10.4 %; ICC 0.70) and cerebral (CV 4.1 %; ICC 0.82) StO2. These data demonstrate good reliability of the majority of physiological variables and indicate that a preloaded 1 500-m time trial conducted in moderate normobaric hypoxia is a highly reliable test of performance. [ABSTRACT FROM AUTHOR]