PURPOSE. To determine whether the ovine eye develops elevation of intraocular pressure (IOP) in response to corticosteroid applied topically. METHODS. IOP was monitored by Perkins applanation tonometry in a group of 18 sheep receiving topically administered 0.5% prednisolone acetate in one eye (experimental), three times daily, for a period of 3 or four 4 weeks after the establishment of baseline IOP values. Perkins readings were converted to actual mm Hg using a calibration curve derived from in vivo manometric measurements. IOP was monitored for an additional 1 to 3 weeks after discontinuation of corticosteroid treatment. RESULTS. Baseline IOP in normal sheep was 10.6 ± 1.4 mm Hg (mean ± SD; n = 36 eyes). The IOP of the experimental eyes began to increase after 1 week of prednisolone treatment in all sheep and reached a peak 1 week later (27.5 mm Hg experimental vs. 11.7 mm Hg fellow, control eye; P < 0.001). After the discontinuation of corticosteroid instillation, the IOP of the treated eyes declined to the baseline values over the course of 1 to 3 weeks. CONCLUSIONS. Ovine eyes exhibit a robust steroid-induced ocular hypertensive response, with 100% occurrence in this trial. The mechanisms of steroid-induced glaucoma may be related to those involved in primary open-angle glaucoma and could provide insight into primary open-angle and clues to its treatment.