The purposes of this study were 1)to investigate the relationship between sprint running performance and isokinetic hip strength, and 2)to clarify the muscles that are important in sprinting from the standpoint of isokinetic strength and muscle cross-sectional area(CSA).Sixteen male(100m sprinting time 10.99±0.46s)and 12 female(12.50±0.44s)subjects ran 60m and their sprinting speed was measured from 30 to 60m.Isokinetic strength of hip and knee flexion and extension(Nm)were mesured at 60, 180 and 300 deg/s.Magnetic resonance imaging(MRI)was used to determine the muscle cross-sectional area of the thigh(upper, middle and lower femur)and trunk.In females, there were no significant correlations between sprinting speed and isokinetic strength.In males, there were significant correlations between sprinting speed and hip strength(absolute value)at all angular velocities(r=0.51-0.75, p<0.05-0.01), except for hip extension at 300 deg/s.Extension at 60 deg/s was significant(r=0.64, p<0.01)only in the male knee.In males, there were significant correlations between the peak torque of hip extension and muscle CSAs of the hamstring and adductor(r=0.50-0.63, p<0.05-0.01), as well as between the peak torque of hip flexion and muscle CSAs of the psoas major and adductor(r=0.59-0.83, p<0.05-0.001).These results suggest that sprint running performance in males is influenced by the strength of hip flexion and extension.In addition, the muscle volume of the hamstring, adductor and psoas major muscles appears to play an important roles during sprint running in males.