Insulin-stimulated 2-deoxy-D-glucose uptake by the rat soleus muscle was concluded to be closely related to Na+/H+ exchanger from the following findings; (1) Insulin stimulated Na+ uptake by rat soleus muscle, (2) Amiloride inhibited the effect of insulin on 2-deoxy-D-glucose uptake by the muscle. (3) External Na+ or Li+ was essential for the action of insulin, and Na+ could not be replaced by other monovalent cations such as K+, Rb+, and choline+. The decreases in the effect of insulin on reduction of the pH of the medium, addition of amiloride, or solution for replacement of Na(+)-Hanks buffer by choline(+)-Hanks buffer could not be explained by decrease in specific binding of insulin.