The spinal and parachordal neurons innervating the trunk muscles and skin in the Japanese eel leptocephali, Anguilla japonica, were retrogradely labeled with a fluorescent dye, DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate). The spinal motoneurons innervating the trunk muscles were located in the medioventral part of the spinal cord and were divided into two populations on the basis of their soma sizes and position. The sensory neurons were labeled in the well-developed dorsal root ganglia, that were situated just peripheral to the meeting of the dorsal and ventral roots. Presumable postganglionic sympathetic neurons were also labeled in the sympathetic ganglia which were located ventrally to the notochord. Thus, the spinal and parachordal neurons innervating the trunk muscles and skin were firstly identified in the anguilliform leptocephalus.