The principle of neurosecretion and the understanding of the hypothalamohypophysial interrelationship, although recently developed, are already well established and of great importance to several medical disciplines. Our knowledge about the function of this system is growing rapidly, but there is still much to be learned about the histology of the neurosecretory hypothalamic nuclei. The generally recognized concept of neurosecretion (Scharrer and Scharrer,1Bargmann,2Heller3) postulates that the neurosecretory hormones are produced by the nerve cells of the hypothalamic nuclei (supraoptic, paraventricular, and infundibular) and descend to the neurohypophysis along their neuraxes, which form the hypothalamohypophysial tract. The neurohypophysis has the mechanism for storage and the regulation of the release of this hormone.4-6 The histological visualization of the neurosecretory substance was made by previous investigators with chrome alum-hematoxylin-phloxine and aldehyde-fuchsin stains, which were developed by Gomori. This neurosecretory material, frequently referred to as the Gomori-positive