• The relationship between the frequency with which 0.125% and 1.0% prednisolone acetate ophthalmic suspensions are instilled and the anti-inflammatory effect they achieve in the cornea was studied. Within the time limits of the experimental protocol, application of the drug at four-hour intervals failed to produce an effect while hourly administration of both concentrations of the corticosteroid produced a substantial anti-inflammatory effect. Instillation at 15-minute intervals resulted in a significantly (P < .05) greater reduction of the polymorphonuclear leukocytes invading the cornea than did administration of the medication every hour. If five doses of prednisolone acetate were applied topically at one-minute intervals each hour, both concentrations of this corticosteroid produced a therapeutic effect in the cornea equal to that achieved by administration of the drug every 15 minutes.