Using methylmethacrylate corrosion microvascular castings, the three-dimensional angioarchitecture of the monkey optic nerve and peripapillary choroid was examined with scanning electron microscopy. The centripetal blood supply to the optic nerve is from a peripheral arterial supply (branches of the short posterior ciliary arteries) toward the central venous drainage (the central retinal vein). Several choroidal branches of the short posterior ciliary arteries also form around the optic nerve a marginal arterial ring, which supplies blood to the peripapillary choroid. Large choroidal veins emerge ~300 (mum away from the margin of the optic nerve and drain this region. Comparison of the anterior optic nerve vasculature of the primate and nonprimate are discussed, and controversies regarding the choroidal involvement in the optic nerve blood supply are revisited.