the present investigation was conducted on the pineal organs of 12 healthy bucks. Sixth samples collected during dark period (at mid night) while the other six collected during light period (at noon).The samples were processed and prepared for light and electron microscopic examination. The pineal organ of bucks was surrounded by a thin fibrous capsule, the pia matter, while the parenchyma was supported by extensive reticular network.The parenchyma of the gland was formed of clusters or groups of pinealocytes intermingled with astroglia cells. Bundles of unmyelinated nerve fibers were noticed in the organ. During dark period the pinealocytes were large in size with finely granular cytoplasm containing well developed rER, mitochondria and many secretory granules. Long branched cytoplasmic processes arised from the pinealocytes to terminate near blood vessels or synapse with a nerve. The pinealocytes reacted positively with antimelatonin antibodies. During the light period the pinealocytes appeared smaller in size with clear non granular cytoplasm. The pinealocytes ahowed a very slight reaction to the antimelatonin antibodies.