¡iAbstract¡j Vagal sensory neurons play an important role in the neural control of airway and other visceral organs. Regional distribution of vagal sensory neurons in the vagal ganglia that correspond to different viscera is uncertain. Horseradish peroxidase (HRP) was applied to the right thoracic vagus nerve and recurrent laryngeal nerve to be retrogradely transported to the neurons in vagal nodose and jugular ganglia. Labeling of neuronal cell bodies was visualized with diaminobenzidine reaction. Ricinus communis agglutinin-60 (RCA-60) was injected into the right thoracic vagus nerve and transported retrogradely to cause destruction of the ribosome in the vagal ganglia neuron cell bodies. The magnitude of neurogenic plasma extravasation induced by capsaicin was measured by the area density of the India ink-labeled leaky blood vessels in the trachea and bronchi. The present study demonstrated that there was no distinct localization of HRP- labeled neurons, except at the level of pharyngeal nerve that was connected to the middle of the nodose ganglion. There were approximately 42.2 % of labeled neurons in the nodose ganglion and 30.5 % in the jugular ganglion 3 days after application of HRP in the thoracic vagus nerve. After application of HRP to the recurrent laryngeal nerve, 13.3 % of labeled neurons was found in the nodose ganglion and 8.3 % in the jugular ganglion. One to two weeks after RCA injection into the thoracic vagus nerve, many cell bodies of neurons had a striking degenerative alteration and the cytoplasmic density was markedly reduced. Nissl¡¦s bodies obviously disappeared and vacuoles were the usual feature. Application of RCA-60 also inhibited the neurogenic plasma extravasation in the right bronchial tree that were reduced by 71- 89 %. It is suggested that RCA- 60 selectively destroyed the vagal sensory neurons that innervated the ipsilateral branchial tree. It is concluded that vagal nodose and jugular ganglia supplied different number of sensory neurons to the vagal branches and regulated the physiological function of the visceral organs.