By means of the rapid Golgi-impregnation technique, intraependymal nerve cells and CSF-contacting neurons were demonstrated in the periventricular layer of the paraventricular nucleus (PVN) of the Japanese quail, chicken and house sparrow. When immunocytochemistry was applied to the brains of Japanese quail, chicken and Pekin duck these cellular elements displayed vasotocin- and neurophysin immunoreactions. In the present material intraependymal and cerebrospinal fluid-contacting neurons of the paraventricular nucleus (PVN) were never stained with antisera against avian vasointestinal peptide (VIP), corticotropin releasing factor (CRF), angiotensin II and serotonin. The periventricular zone of the PVN comprises conspicuous fiber networks immunoreactive with antisera to neurophysin, vasotocin and CRF. Our results indicate a general morphologic pattern of the above-mentioned peptidergic systems in all avian species investigated, irrespective of their taxonomic position or of certain peculiarities of the habitat and functional adaptation. The present neuromorphological results may provide a basis for further functional analysis of the interrelationships between the compartments containing cerebrospinal fluid and the neuroendocrine hypothalamic centers involved in various autonomic control mechanisms.