We observed the autonomic nerve plexuses in the skin of an erythermalgic patient and a normal individual using the methods of acetylcholinesterase (AChE) histochemistry, catecholamine histofluorescence, and electron microscopy. The density of both AChE-positive and catecholamine-containing nerve terminals in the periarterial and sweat glandular plexuses was greatly reduced in the erythermalgic foot skin compared with those in unaffected skin from the same patient and in the foot skin of a normal individual. Ultrastructurally, the terminal axons containing either agranular (cholinergic) or small dense-cored (adrenergic) vesicles were present in the periarterial and periglandular regions of the erythermalgic skin, but the occurrence of these nerve terminals in the involved skin appeared to be much reduced in frequency compared with uninvolved skin and the skin of a normal individual.