Sustained intraocular pressure elevations were induced in 15 monkey eyes by argon laser photocoagulation of the trabecular meshwork. Large fluctuations of IOP resulted. Posttreatment gonioscopy revealed an open angle with scattered low peripheral anterior synechiae. Optic disc cupping progressed during pressure elevations, manifested first as posterior bowing of the optic nerve head and peripapillary tissues. Reversal of this early phase of cupping occurred in eight eyes during spontaneous normalization of IOP. In most eyes, as cupping evolved from saucerization to a deeper cup, the cup remained round. In four eyes, focal sloping of the cup to the inferotemporal rim occurred with nerve fiber layer defects. Total cupping with undermining of the rim occurred in five eyes with prolonged IOP elevation. Laser-induced primate glaucoma has features in common with juvenile human glaucoma and is a useful model for the study of cupping of the optic nerve head.