Steady-state mRNA levels and immunoreactive proteins for high- (p140trk) and low-affinity nerve growth factor receptor (LNGFR) in the adult and aged human peripheral nervous system (PNS) were examined in autopsied material. trk mRNA expression was observed only in the sympathetic and dorsal root ganglia, while LNGFR mRNA was expressed widely through the PNS as well as non-neural tissues. Immunoreactive trk proto-oncogene product (p140trk) and LNGFR occurred in the perikarya of the subset of the sympathetic and dorsal root ganglion neurons, but only LNGFR immunoreactivity also occurred in the perineurium and the outer layer of the vessels. The spatial patterns of the trk and LNGFR gene expression in the adult human PNS were similar to those observed in the rat, mouse and chick, and their expression was well preserved in the aged.