Batista, MB, Valente-dos-Santos, J, Duarte, JP, Sousa-e-Silva, P, Coelho-e-Silva, MJ, Werneck, AO, Ohara, D, Cyrino, ES, and Ronque, ERV. Independent and combined effects of weight status and maturation on aerobic fitness in adolescent school-aged males. J Strength Cond Res 34(9): 2663-2671, 2020-This study aimed to examine the independent and combined effects of pubertal and weight status on concurrent measurements of peak oxygen (V[Combining Dot Above]O2peak) in school-aged adolescent males. The final sample included 49 boys (12.3 ± 0.8 years). V[Combining Dot Above]O2peak was derived from an incremental progressive maximal protocol using a motorized treadmill. In addition, maximal oxygen uptake was estimated from a 20-m shuttle run test. Static allometric models were obtained as an alternative to performance output per unit of size descriptors. Weight status had a significant effect on V[Combining Dot Above]O2peak using simple ratio standards per unit of body mass (BM) with adolescents classified as overweight and obese (OWOB) attaining lower values of V[Combining Dot Above]O2peak. A similar trend was noted for the allometric models adopting body mass (ml·kgBM·min), stature (L·m·min), and fat-free mass (FFM; ml·kgFFM·min). Findings also suggest the influence and interaction of pubertal and weight status on absolute values of V[Combining Dot Above]O2peak. Considering the data obtained, linear equations to estimate V[Combining Dot Above]O2peak from the 20-m shuttle run test should not be applied to boys who are OWOB because it will produce inaccurate assessments of cardiorespiratory fitness and penalize those who are heavier. Equations for V[Combining Dot Above]O2peak prediction need to be specific for pubertal status and preferably consider FFM as a body size descriptor.