The medullary nuclei and the primary projections of the octaval nerve have been studied in the Teleost Chelon labrosus, using argentic impregnations, NISSL stains and anterograde marking with peroxidase. The octaval nerve enters the medulla in two separate branches, the anterior and posterior. In its intramedullary traject it originates ascendent and descendent bundles. Its fibres end principally in the ventral part of the octavo-lateral area, with practically no overlapping with the terminals of the lateral line nerves. Three neuronal groups appear in this zone: the magnocellular vestibular nucleus, the tangential nucleus and the descending octaval nucleus. The magnocellular nucleus, formed by large neurons, receives thick fibres from the anterior branch of the octaval nerve. The tangential nucleus can be subdivided into three parts: Dorsal, intermediate and ventral depending upon its afferents and efferents. The dorsal part receives fibres from the posterior root of the octaval nerve. Fibres from the anterior branch end in the intermediate and ventral parts. The descending octaval nucleus, formed by polymorphous neurons, receives descending fibres from the octaval nerve branches. These fibres form a peculiar neuropil. A few fibres from both branches end in the medial nucleus of the octavolateral area. No primary projections of the octaval nerve have been found to the cerebellar crests.