Location of origin cells of efferent fibers in the rabbit superior and inferior laryngeal nerves was investigated in association with their soma size, using the horseradish peroxidase (HRP) retrograde labeling technique. The nucleus ambiguus (nA) of the rabbit displays a different cytoarchitectonic appearance in its rostral fourth and caudal three-fourths, the former of which consists of a defined group of neurons (CG) with a compact arrangement and an undefined neuron group (SG) scattered around CG. On the other hand, the caudal three-fourths of nA is formed by a neuron group with a scattered arrangement similar to SG. Origin cells of the superior laryngeal nerve were confined to CG and SG of the rostal fourth of nA and a much smaller number also existed in the dorsal vagal nucleus. The mean some sizes of the CG and SG neurons were 18±2.6μm and 24±2.6μm, the former being smaller than the latter. Origin cells of the inferior laryngeal nerve were located in DG of the caudal three-fourths of nA, and their mean soma size was 26±3.3μm, indicating a difference of intra-nA localization and soma size between origin cells of the superior and inferior laryngeal nerves.