This study attempted to clarify the relationship between the muscle size of the triceps surae and the cross-sectional area (CSA) of the Achilles tendon (AT) in sprinters. The subjects were 10 collegiate sprinters (years of sprint training: 8.7±1.6 yr) and seven age-matched controls. Serial cross-sectional T1-weighted magnetic resonance images of both legs were taken using a magnetic resonance imaging system. Maximum CSA of the AT, gastrocnemius and soleus muscle, and muscle volume of the triceps surae were measured and compared between the two groups. The values of maximum CSA of the AT, gastrocnemius and triceps surae muscle and the volume of all muscles of sprinters were significantly larger than those of control subjects. However, maximum CSA of the soleus muscle did not differ significantly between the groups. The relationship between each muscle size and maximum CSA of the AT differed between the left and right. However, the maximum CSA of the AT was highly correlated with muscle volume of the triceps surae rather than the maximum CSA of each muscle in every leg in both groups. The regression lines for muscle volume of the triceps surae against the maximum CSA of the AT differed significantly between the groups. Therefore, it was suggested that the maximum CSA of the AT of sprinters was correlated with the muscle volume of the triceps surae.