We produced intraocular pressure (IOP) elevations in 32 primate eyes and studied retinal ganglion cell rapid axonal transport with autoradiography and electron microscopy. Animals breathing room air at sea level pressure were compared to animals breathing 100% oxygen at 3 atm pressure in a hyperbaric chamber. Despite major increases in arterial oxygen levels in the hyperbarically oxygenated animals, both groups had axonal transport blockade at the optic nerve head. Anoxia appears not to be the most important cause of acute axonal damage induced by elevated IOP. The pattern of axonal abnormality within individual fiber bundles at the optic nerve head provides support for mechanical compression as a more likely alternative cause for induced neural damage.