Hsu, CC, Fong, TH, Chang, HM, Su, B, Chi, CP, Kan, NW, and Hsu, MC. Low second-to-fourth digit ratio has high explosive power? A prepubertal study. J Strength Cond Res 32(7): 2091-2095, 2018-A recent study reported that lower limb explosive power had no correlation with the index finger: ring finger (2D:4D) ratio. However, many studies hypothesized that a lower 2D:4D ratio (reflecting a relative higher testosterone exposure) predicts higher physical fitness. The aim of this study was to replicate the study of explosive power and the 2D:4D ratio in a sample of Taiwanese children. A total of 541 Taiwanese prepubertal children (257 girls and 284 boys aged 9-10 years) participated in this study. This study analyzed the relationship between the 2D:4D ratio and explosive power. Explosive power of the lower limbs was assessed using the standing long jump (SLJ) test. The lengths of the second and fourth fingers of the right hand were measured to calculate the 2D:4D ratio. The SLJ length was correlated with the 2D:4D ratios (r = -0.144, p = 0.015) in boys. After controlling for age and the body mass index, this correlation remained significant (r = -0.134, p = 0.024). For girls, 2D:4D ratios were not significantly correlated with SLJ scores. These results indicate that the SLJ distance was negatively correlated with the 2D:4D ratio in boys, but not in girls. These findings might suggest that prenatal testosterone exposure is negatively correlated with the explosive power in men, but not in women.