The purpose of the study was to assess straight sprinting, change of direction ability and horizontal jump performance in youth runners according to age and gender. Two hundred and fifty-five youth runners (116 boys and 139 girls) participated in this study. The athletes were divided according to their age into five groups: under 8 yr (U8), under 10 yr (U10), under 12 yr (U12), under 14 yr (U14) and under 16 yr (U16). Significant differences (p < 0.01) were found between U8 and U10 in the 5 m sprint (d = 1.22), 505 agility test (505, d = 0.96), modified agility test (MAT, d = 1.43), horizontal countermovement jump (HCMJ, d = 1.06) and arm swing HCMJ (HCMJAS, d = 1.44); between U10 and U12 in the 505 (d = 0.39), MAT (d = 0.74), HCMJ (d = 0.96) and HCMJAS (d = 0.75); and between U12 and U14 in 5 m (d = 0.84), HCMJ (d = 0.88) and HCMJAS (d = 0.79). However, no significant differences (p > 0.05, d = 0.29-1.17) between U14 and U16 were observed in any of the tests. With regard to age and gender, in U8 and U10 groups there were no significant differences (p > 0.05, d = 0.02-0.76) between boys and girls in any test. However, in U12 and U14 groups, significant gender differences (p < 0.05, d = 0.85-1.24) were found in the MAT. Likewise, the boys obtained better results than girls in the horizontal jump tests (p < 0.05, d = 1.01-1.26). After the classification by age, some differences were observed between both genders, depending on the fitness variable evaluated.