Tetrodotoxin-resistant sodium currents contribute to the somal and axonal sodium currents of small diameter primary sensory neurons, many of which are nociceptive. NaN is a recently described tetrodotoxin-resistant sodium channel expressed preferentially in IB4-labeled dorsal root ganglion (DRG) neurons. We employed an antibody raised to a NaN specific peptide to show that NaN is preferentially localized along axons of IB4-positive unmyelinated fibers in the sciatic nerve and in axon terminals in the cornea. NaN immuno-reactivity was also found at some nodes of Ranvier of thinly myelinated axons of the sciatic nerve, where it was juxtaposed to Kvl. 2 potassium channel immunoreactivity. This distribution of NaN is consistent with a role for NaN sodium channels in nociceptive transmission.