The carotid rete-cavernous sinus complex of sheep and goat (adult and feti) was investigated. Intra vascular injection materials (Latex, Batson's #17 and Decopour) were employed to describe the blood vessels of this structure. Further, paraffin embedded sections were stained with Harris' hematoxylin and eosine, Van Gieson's, Gomori one-step trichrome and Weigert. After maceration, injected vessels were used to study the carotid rete-cavernous sinus complex with scanning electron miroscope (SEM). In addition, aldehyde fixed, cryofractured complexes were studied with the SEM. The complex was sectioned with the cryostat and several laboratory procedures were performed to detect the presence of alkaline phosphatase (A.P.), 5('-)-nucleotidase (5('-)-N) and adenosine triphosphatase (ATP-ase) enzymes;Gross study revealed that the carotid rete was supplied with blood by one caudal rete branch, and two to four rostral rete branches were thought to be normal. The extracranial portion of the internal carotid artery was postnatally absent in both sheep and goat specimens. Light microscopic examination showed that the carotid rete branches were medium-sized, muscular arteries. These arterial branches shared a common tunica adventitia with the cavernous sinus. The carotid body cells were observed in an aberrant position (intracranially in the wall of the internal carotid artery) due to regression of the extracranial portion of the internal carotid artery after birth. The cavernous sinus, on the other hand, showed variations in thickness of the wall from region to region. In some areas, the cavernous sinus had smooth muscle cells in the tunica media while in other areas only connective tissue and endothelial cells were noticed;The carotid rete-cavernous sinus complex of sheep was easily filled with both Batson's #17 and Decopour as seen by SEM. Craters were observed in the endothelial lining of the carotid rete branches but not of the carvernous sinus;Finally, a minute amount of A.P. enzyme was demonstrated in the walls of the carotid rete-cavernous sinus complex. But, 5('-)-N was found in large quantities in the endothelial cells and the tunica adventitia of both the branches of the carotid rete and the cavernous sinus, though it was absent in the tunica media of the carotid rete branches. Varying quantities of ATP-ase was demonstrated in all layers of carotid rete branches and the cavernous sinus. The amount of this enzyme appeared larger towards the lumen and gradually decreased towards the peripheries in the arterial branches as well as the cavernous sinus.