While there is a direct relationship between maximal anaerobic power (Pmax) and swimming performance, the relationship between upper and lower limbs with regard to Pmax and force-velocity (F-v) characteristics is not clear. The aim of the present study was to examine the effect of age and sex on the ratios of mechanical characteristics between upper and lower extremities of adolescent swimmers. Seventeen girls (aged 14.7±1.8 yr) (mean±standard deviation) and 28 boys (14.6±1.4 yr), all members of competitive swimming clubs, performed a F-v test for both legs and arms. In legs, boys had higher values of Pmax (t43=2.4, p<0.05), Pmax expressed in relative to body mass values (rPmax, t43=3.4, p<0.01) and v0 (t43=4.3, p<0.001), while no differences were found for F0 (t43=1.0, p=0.31) and v0/F0 (t43=0.55, p=0.59). In arms, boys had higher values of Pmax (t43=3.2, p<0.01), rPmax (t43=3.9, p<0.001) and v0 (t43=3.4, p<0.01), while no differences were found for F0 (t43=1.9, p=0.06) and v0/F0 (t43=0.16, p=0.87). However, no sex difference was found with regard to the ratios of Pmax (t43=1.9, p=0.06), F0 (t43=1.2, p=0.23) and v0 (t43=1.3, p=0.20) between upper and lower extremities. There was direct relationship between age and Pmax of legs (r=0.64, p<0.01 in girls; r=0.43, p<0.05 in boys) and arms (r=0.56, p<0.05; r=0.57, p<0.01 respectively), while there was not any significant association between age and the ratios of mechanical characteristics of upper and lower limbs. These findings emphasize the need for separate evaluation of arms' and legs' force-velocity characteristics on a regular basis and the consideration of these measures in training design.