Choline acetyltransferase immunocytochemistry was used to detect the presence and distribution of cholinergic through-fibers in the superior cervical ganglion of adult mice. The results revealed a great number of choline acetyltransferase-positive axons in the cervical sympathetic trunk and the varicose terminal axons involved in the innervation of the principal ganglionic cells within the ganglion. Immunostained axons were scarce or absent in the external or internal carotid nerves. The immunocytochemical results argue against the physiological importance of cholinergic through-fibers in the postganglionic nerves.