The purpose of this study was to assess the reproducibility of running time to exhaustion (Tlim) at maximal aerobic speed (MAS: the minimum speed that elicits VO2max), on eight subelite male long distance runners (29 +/- 3-yr-old; VO2max = 69.5 +/- 4.2 ml.kg-1.min-1; MAS = 21.25 +/- 1.1 km.h-1). No significant differences were observed between Tlim measured on a treadmill at a 1-wk interval (404 +/- 101 s vs 402 +/- 113 s; r = 0.864); however, observation of individual data indicates a wide within-subjects variability (CV = 25%). In a small and homogenous sample of runners studied, exercise time to exhaustion at MAS was not related to VO2max (r = 0.138), MAS (r = 0.241), running economy (mlO2.kg-1.min-1 at 16 km.h-1) (r = 0.024), or running performance achieved for 3000 m (km.h-1)(r = 0.667). However, Tlim at MAS was significantly related to the lactate threshold determined by the distinctive acceleration point detected in the lactate curve around 3-5 mmol.l-1 expresses in %VO2max (r = 0.745) and to the speed over a 21.1-km race (km.h-1) (r = 0.719). These data demonstrate that running time to exhaustion at MAS in subelite male long distance runners is related to long distance performance and lactate threshold but not to VO2max or MAS.