A The front side of the sphenoid relates to the optic decussation, the frontal, and the maxillary nerve (MN); the external side of the sphenoid relates to the optic nerve (ON), internal carotid artery (ICA), maxillary nerve, the pituitary fossa (PF); the posterior relates to the PF and sella turnica; its external wall relates to the cavernous sinus, ICA, and cranical nervers III, IV, V, VI Objectives: Describe and measure dimentions of the sphenoid and related structures. Method: A design of descriptive, cross sectional study in 30 half skulls of VietnameseResults: 76.6% of the half skulls had one sphenoid ostium, and 6.7% had two in the same side.