Abstract The aim of the study was to examine supramaximal intermittent running performance in highly-trained young soccer players, with regard to age and locomotor profile. Twenty-seven Under 14, 19 U16 and 16 U18 highly-trained soccer players performed an incremental intermittent running test (30-15 Intermittent Fitness Test) to assess supramaximal intermittent running performance (V_IFT), an incremental running test to estimate maximal aerobic speed (V_Vam-Eval) and a 40-m sprint to estimate maximal sprinting speed (MSS). U16 and U18 presented very likely greater V_IFT (19.2 ± 0.9, 19.7 ± 1.0 vs. 17.4 ± 0.9 km · h^-1) and V_Vam-Eval (16.2 ± 0.9, 16.7 ± 1.0 vs. 14.6 ± 0.9 km · h^-1) than U14, while there was no clear difference between U16 and U18. MSS (25.1 ± 1.6, 29.3 ± 1.6 and 31.0 ± 1.1 km · h^-1 for U14, U16 and U18) was very likely different between all groups. When data were pooled together, V_IFT was very largely correlated with V_Vam-Eval and MSS (overall r =0.89, partial r = 0.74 and 0.29, respectively). Within-age group correlations showed that the older the players, the greater the magnitude of the correlations between V_IFT and V_Vam-Eval (r = 0.67, 0.73 and 0.87). In conclusion, the major predictors of V_IFT were, in order of importance, V_Vam-Eval and MSS; however, the older the players, the greater the correlations with V_Vam-Eval.