AbstractThe hypothalamo‐neurohypophyseal system of the catfish, as revealed byin situtechniques, consists of the prominent nucleus preopticus, the axonal tracts, and the neurohypophysis. The preoptic nucleus, which is composed of the pars magnocellularis and the parvocellularis, is situated on either side of the optic recess slightly anterior to the optic decussation. Axons arising from the nucleus preopticus form two ventro‐lateral tracts; bundles of axons separate out from these tracts at 10 to 12 points and extend medially to form two ventro‐medial tracts lying on either side of the optic recess. The ventro‐lateral and ventro‐medial tracts eventually merge slightly anterior tc the hypophysis to form the infundibular stalk which penetrates the pituitary and ramifies. The nucleus lateralis tuberis is situated rostral and antero‐ventral to the third ventricle and their axons join the ventro‐medial tracts.The arterial supply to the hypophysis is through a median hyophyseal vessel whose branches penetrate the pituitary along with the infundibular stalk and follow the ramifications of the neurohypophysis. A portal circulation between the hypothalamus and the hypothalamus