The maximum aerobic speed (MAS), the speed corresponding to the maximal steady state v̇O2max, is usefull for training purposes. The Université de Montreal Track-Test (Léger and Boucher, 1980) and the 20 − m shuttle run test (Léger et al, 1984) allow the measure of the MAS and the estimation of the maximal oxygen uptake (v̇O2 max). However, if v̇O2 max estimated by these two field tests appears to be close and well correlated to laboratory measurement of v̇O2 max according to previous studies (Léger and Boucher, 1980; Léger et al., 1984, Gadoury and Léger, 1986; Poortmans et al, 1986; Prat et al, 1986; Van Mechelen et al, 1986; Paliczka et al, 1987; Ramsbottom et al, 1988), the MAS was found lower in the 20 − m shuttle run test by Gerbeaux et al (1991). It was thus decided to look more closely to theses relationships both with college students (G1:n = 266, 13.5 yr old) and physical education students (G2:n = 17, 22.6 yr old). All subjects performed the two field tests while subjects of G2 performed a treadmill test for direct v̇O2max measurement. For the three tests, initial speed was set at 8 km·h−1. The track-test was performed on a 400 − m track with markers every 25 m; speed increment was 1 km·h−1 per 2-min stage. For the 20 − m shuttle run test, speed increment was 0.5 km·h−1 per 1 − min stage. And for treadmill test (3% slope), the speed was increased by 2 km·h−1 per 4 − min stages. For each test, a short-range telemetry system (Sport Tester PE 3000) is used to record heart rate and blood samples are taken during the two-minute period following the end of the exercise. For G2, The lactate concentration (> 12 mmol.l−1) and the maximum heart rate (> 190 bpm) after the field tests reach commonly accepted levels for v̇O2max (Davies et al, 1984). The average maximum speed at the shuttle run test (11.2 km·h−1 ± 1.01 for G1 and 13.1 km·H−1 ± 0.99 for G2) are significantly lower (P < 0.01) to that of the track-test (12.4 km·h−1 ± 1.82 for G1 and 15.8 km·h−1 ± 1.91 for G2). The speed difference between the two field tests increases proportionally to the fitness of the subjects (fig 1). The regression line between the maximal speeds achieved during these two field tests are: MAS (track-test) = 1.34*MAS (Shuttle) −2.86 (r = 0.75) for G1 and MAS (track-test) = 1.81*MAS (shuttle) −7.86 (r = 0.93) for G2. For G1, estimated v̇O2 max from the track-test (54.4) ml·kg−1.min−1 ± 6.79) and the 20 − m shuttle run test (51.1 ml·kg−1.min−1 ± 5.93) are lower (P < 0.01) than treadmill measured v̇O2 max (58,8 ml·kg−1.min−1 ± 7.10) and, this appears independant of the performance level (fig 2). The maximum speed achieved during the two field tests are different. However, the strong correlation which exists between these values indicates that it is possible to predict one from another.