Chronic elevations of intraocular pressure (IOP) were produced in rabbit and monkey eyes by anterior chamber injection of autologous fixed red blood cells. The method confirms the possibility of secondary glaucoma due to trabecular obstruction by ghost cells in eyes with intraocular hemorrhage. In primates, decreased aqueous outflow may result from direct obstruction by free cells and macrophages as well as swelling of trabecular endothelium following phagocytosis of cellular debris. IOP elevations for from 2 days to greater than 1 month were produced in order to study the effects of elevated IOP on ocular tissues. The model has the advantages of producing IOP elevation easily and without associated intraocular inflammation. The extensive filling of the anterior chamber necessary to produce IOP rises in healthy animal eyes leads to the disadvantage of poor visibility of the optic disk. In rabbit eyes, chronic IOP elevation leads to corneal enlargement and ectasia, making IOP measurements difficult.