The autoradiographic localizations of opiate and histamine H1-receptors were studied quantitatively and compared following dorsal root section in the primate spinal cord. High densities of opiate and H1-receptors were found in the superficial layers of the dorsal horn. Dorsal root section produced a 40-50% loss of both receptors types throughout layers I and II with no loss in deeper layers of the dorsal horn. "Bursts' of opiate and H1-receptor labelling was observed over a population of small diameter cells (35-45 micron or micrometer) in the primate dorsal root ganglion. These cells represented approximately 8% of the total cells present. Serial consecutive sections demonstrated a population of cells bearing both opiate and histamine H1-receptors.