Aim. The purpose of this study was to verify the effect of biological maturation on soccer players' maximal oxygen uptake (V̇O2max) and ventilatory breakpoint (VB) expressed in three different forms. Methods. Thirty-seven male amateur athletes (14 years old) were divided according to Tanner's maturational degree into three groups, prepubescent (PreP), pubescent (Pub) and post-pubescent (PostP). Ventilation, ventilatory equivalents, respiratory exchange ratio were measured by indirect calorimetry. TheV̇O2max was expressed in absolute values, relative to body mass and according appropriate scaling procedures. First ventilatory breakpoint (VB1) and second ventilatory breakpoint (VB2) were used as index of aerobic and anaerobic thresholds. Results. WhenV̇O2 was expressed in absolute terms, difference among groups was found in V̇O 2max and VB2, with PostP having higher values compared to PreP and Pub. There was no difference among groups inV̇O2 when it was expressed as relative form inV̇O2max (49-9±3.1, 50.0± 3.0 and 49.8±2.9 for PreP, Pub and PostP respectively) and VB2, however PreP showed a higher VB1 than both Pub and PostP. There was difference among groups inV̇O2 expressed according to allometric scaling at V̇O2max (126.9±0.9, 136.4±8.6 and 139.9±9,1for PreP, Pub and PostP respectively) and VB1. The difference was verified at VB2 only between PreP and PostP. Conclusion. In conclusion, biological maturation affects young soccer players' VB1, VB2, V̇O2max, and the allometric expression seems to be the more appropriate to adjust the effects of body mass.