The influence of sexual maturation on the Wingate anaerobic test performance of 100 boys and 100 girls, ages 12.2 ± 0.4 years, was examined using Tanner's indices of pubic hair and, in boys, salivary testosterone as measures of maturation. No sex differences (p > .05) in either peak power (PP) or mean power (MP) were revealed. Significant main effects (p < .01) for maturation were detected for both PP and MP expressed in W, W · kg-1, or with body mass controlled using allometric principles. Testosterone did not increase the variance in PP or MP explained by body mass alone (p > .05). No sex or maturational effects were observed for postexercise blood lactate (p > .05). Testosterone was not (p > .05) correlated with blood lactate. Thus, sexual maturation exerts an influence on PP and MP independent of body mass, but maturational effects on postexercise blood lactate remain to be proven in this age group.