Mutations in the myelin protein zero gene (MPZ) are associated with certain demyelinating neuropathies, and in particular with Charcot-Marie-Tooth disease type 1B (CMT1B), Dejerine-Sottas syndrome, and congenital hypomyelination. MPZ mutations affecting the protein's transmembrane domain are generally associated with more severe phenotypes. We describe a family with mild CMT1B associated with a transmembrane MPZ mutation. Sequence analysis identified a G-to-C transversion at nucleotide 1064, predicting a glycine-to-arginine substitution in codon 163 (G163R) of MPZ. This report furthers the understanding of the clinical and electrophysiological manifestations of MPZ mutations.