This article reviews the distribution of S100 proteins in the human peripheral nervous system. The expression of S100 by peripheral glial cells seems to be a distinctive fact of these cells, independently of their localization and their ability to myelinate or not. S100 proteins expressing cells include satellite cells of sensory, sympathetic and enteric ganglia, supporting cells of the adrenal medulla, myelinating and non-myelinating Schwann cells in the nerve trunks, and the Schwann-related cells of sensory corpuscles. In addition, S100 proteins are expressed in peripheral neurons. Most of them express S100α protein, and a subpopulation of sensory neurons in dorsal root ganglia contains S100β protein or S100α plus S100β proteins. Microsc. Res. Tech. 60:633–638, 2003. © 2003 Wiley-Liss, Inc.