To investigate the effects of the acute exercise and the long-term aerobic training on carnitine concentration in skeletal muscle, we made Sprague-Dawley rats undergo the acute exercise and the long-term aerobic training (20-25 m/min, 10˚ incline, 60 min/day, 5 days/week, 12 weeks), then finally we came to conclusion like this. TC of liver decreased significantly in the AA (after 12 weeks acute exercise) group and the LE (12 weeks long-term exercise) group than in the AC (after 12weeks control) group (p＜.05). The concentration of free carnitine in soleus muscle increased significantly in the LE group than in the AC group. In red-type gastrocnemius muscle, the concentration of free carnitine and total carnitine decreased significantly in the AA group, but increased significantly in the LE group, so consequently those kept the level of AC group (p＜.05). In white-type gastrocnemius muscle, the concentration of long chain acylcarnitine increased in the AA group and LE group than in the AC group, especially increased in AA group (p＜.05). In other hand, there was no difference among the groups in plantaris muscle. Camitine is quaternary amine related deeply with the aerobic metabolism, and their activation in coleus muscle, and red-type gastrocnemius muscle increased significantly. In this result, we can suppose that soleus muscle and red-type gastrocnemius muscle are consisted of suitable muscle fiber for aerobic metabolism.