Hyperosmotic agents (2 M urea or 2 M DL-lactamide), perfused into the internal carotid artery of Rhesus monkeys, produced a marked decrease in intraocular pressure and an increase in aqueous humor protein. Fenestrae of the ciliary capillaries were broken immediately following the perfusion and the nonpigmented epithelium was separated from the pigmented epithelium. The pigmented epithelium especially of the pars plana then became degenerative. As intraocular pressure began to rise slowly, three to seven days after perfusion, the nonpigmented epithelium recovered to an almost normal structure, but the pigmented epithelium did not regenerate. The surviving cells in the pars plicata formed the original apico-apical junctions. The number of vacuoles in the endothelium of Schlemm's canal decreased while the intraocular pressure was low and increased gradually with the recovery of the intraocular pressure.