The fine structure of the caudal neurosecretory system in Raia batis was studied. Far-reaching similarities with ultrastructural details of other vertebrate neurosecretory systems were noted. The secretion is present in all parts of the system in the form of elementary neurosecretory granules which seem to be formed in the Golgi complex of the cell body. The morphology of the terminal region is discussed in relation to the possible mode of secretion release and in connection with the routes of secretion to the vascular lumen.