This study examined the relationships among concentric isokinetic knee flexor, extensor ratios (F/E ratios), peak torque (PT) and performance in long jumpers. Eighteen subjects participated in this study. All subjects performed three (60°/s) and five (120°/s, 180°/s and 240°/s) maximal knee extension and flexion efforts of both legs under concentric conditions. Pearson Product Moment Correlation analyses were conducted to determine the relationships among the peak torque, flexor/extensor ratios and long jump performance. The significance level was set at p<.05. The average torque at 60°/s, 120°/s, 180°/s and 240°/s were 227.80±21.83 Nm、178.84±26.13 Nm、148.69±26.09 Nm、121.04±30.60 Nm in knee flexor and 148.77±21.88、137.13±18.57、121.72±16.15、100.53±21.22Nm in knee extensor, respectively. The F/E ratios ranged from 65.60 to 93.84%. The peak torque decreased as the velocity of the test increased, but the F/E ratios increased as the velocity of the test increased. There were, however, no significant relationships between the PT, F/E ratios and long jump performance (p>.05). In conclusion, coaches and long jumpers may use these findings in evaluating and planning exercise programs during training and rehabilitation.