To evaluate the role of topical instillation of anti-inflammatory or antiallergic agents on experimental elevation of aqueous flare induced by prostaglandin E 2 (PGE 2) in pigmented rabbits. Methods: Transcorneal diffusion of PGE 2 , 25 µg/mL (7.09ϫ10 −2 mmol/L), by means of a glass cylinder produced aqueous flare elevation. Anti-inflammatory or antiallergic agents were topically administered once or twice before PGE 2 application. Aqueous flare was measured with a laser flare-cell meter. Results are given as mean±SD. Results: Double instillations of 0.1% betamethasone sodium phosphate and 0.1% fluorometholone acetate at 4 and 2 hours before PGE 2 application inhibited 61%±11% and 46%±14%, respectively, of flare elevation. Double instillations of 0.1% diclofenac sodium and 0.1% pranoprofen at 4 and 2 hours before PGE 2 application did not inhibit flare elevation. Double instillations of 0.1% betamethasone, 0.1% fluorometholone, 0.1% diclofenac, and 0.1% pranoprofen at 1 and 0.5 hour before PGE 2 application inhibited 16% ± 10%, 16% ± 6%, 24% ± 9%, and 23%±10%, respectively, of flare elevation. Double instillations of 2% cromolyn sodium, 0.5% tranilast, 0.025% levocabastine hydrochloride, 0.1% pemirolast potassium, and 0.01% ibudilast at 1 and 0.5 hour before PGE 2 application did not inhibit flare elevation. Single instillation of 0.1% betamethasone 6 hours before PGE 2 application inhibited 88% of PGE 2-induced aqueous flare elevation. Single instillation of 0.1% diclofenac 1 hour before PGE 2 application inhibited 23% of PGE 2induced aqueous flare elevation.