The origin and course of hypothalamic neurosecretory tracts is demonstrated byin situ staining procedure. Both Pars parvocellularis and Pars magnocellularis, components of nucleus preopticus, contribute to the formation of the right and left main neurosecretory tract. Anteriorly the tract is loosely assembled and formed of 3 subsidiary tracts which later join at the level of horizontal commissure to form a thick consolidated single tract. From the main tract several bundles of axons are given towards the mid-ventral region at the point of curvature to form ventromedian tracts. The ventromedial and the main tract of each side jointly enter the pituitary, anterio-dorsally.