The subject of the blood supply of the optic nerve head (ONH) is reviewed briefly. The circulation of the posterior ciliary artery is the main source of blood supply to the ONH, except for the surface nerve fiber layer which is supplied by the retinal circulation. The blood supply in the ONH is sectoral in nature, which is the reason why there is the sectoral involvement of the ONH in its ischemic disorders. It is essential to understand that the pattern of blood supply in the ONH shows marked interindividual variation, and so consequently does the pattern of visual loss in its ischemic disorders. The venous drainage from the ONH is by the central retinal vein. Reasons for various controversies on the subject are discussed.