In this study, we electron-microscopically investigated a number of sympathetic axons in the arteriolar walls of the extensor digitorum longus muscles of the rat rear leg. Arterioles in the muscle were divided into two groups: (i) one group consisted of arterioles with accompanying muscle spindles, and (ii) the other consisted of arterioles without accompanying muscle spindles. The number of sympathetic axons present in the arteriolar walls and the ratios to the total number of sympathetic and non-sympathetic axons were compared between the groups. For electron-microscopic identification of sympathetic axons, 5-hydroxydopamine, a pseudotransmitter agent, was used. The number and ratio of sympathetic axons were significantly higher in arterioles with accompanying muscle spindles than arterioles possibly unrelated to muscle spindles. Additionally, amine- and immunohistochemistry were used to confirm the above observation.