The acetylcholine synthesizing (ACh-s) activity and the binding of the nicotine ligands 3H-alpha-bungarotoxin (alpha Btx) and 3H-d-tubocurarine (d-TC) were analysed in rat hind limb muscles 1-32 days after denervation. Muscles of the contralateral leg served as controls. ACh-s activity was considerably lower in tibialis anterior as compared to the extensor digitorum longus and the peroneus longus muscles. After denervation there was a rapid decrease in ACh-s activity in parallel to a considerable increase in alpha-Btx binding. The binding of d-TC was essentially unchanged following denervation indicating the special characteristics of the newly formed receptors. ACh-s activity can be differentiated into one specific (choline acetyltransferase) and one unspecific component.