The aim of this investigation was, first, to examine comparatively the changes in first and second ventilatory thresholds (VT1 and VT2 ) and, secondly, to compare with peak oxygen uptake (${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $) changes following high-intensity interval training (HIT) in prepubescent children. Eighteen prepubescent children (aged 10.1 ± 0.7 years) performed an incremental exhaustive exercise on a cycle ergometer with pulmonary gas exchange measurements before and after an 8-week period. During this period, nine children (five girls and four boys; initial ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $: 39.6 ± 6.0 ml O2  · min(-1)  · kg(-1) ) took part in a HIT and nine other children (three girls and six boys; initial ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $: 39.8 ± 7.8 ml O2  · min(-1)  · kg(-1) ), considered as controls, were not trained. After the training period, VT1 , VT2 , and ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $ were significantly (P < 0.01) improved (21%, 24%, and 14%, respectively) without significant changes in the control group. However, the changes in VT1 (ΔVT1 = +4.35 ± 4.36 ml O2  · min(-1)  · kg(-1) ), VT2 (ΔVT1 = +7.17 ± 5.17 ml O2  · min(-1)  · kg(-1) ), ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $ ($\Delta {\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $ = +5.51 ± 4.17 ml O2  · min(-1)  · kg(-1) ) induced by HIT in trained children were not related. In conclusion, for prepubescent children, in addition to VT1 and ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $, VT2 can also be significantly improved by training. Therefore, HIT represents a good way to obtain great improvement in these parameters in only 8 weeks. However, the time courses of these aerobic fitness parameters are dissociated, which implies the need to differentiate among them during aerobic fitness exercise testing.