Aqueous protein content was estimated as a measure of the integrity of the blood-aqueous barrier after paracentesis or argon laser photocoagulation of the iris in rabbits. Corticosteroid pretreatment topically or by subconjunctival or intramuscular injection exerted only a moderate inhibitory effect on the breakdown of the bloodaqueous barrier. Instillation of 0,1% indomethacin however, strongly inhibited the response in both models. The results are indicative of the potential usefulness of topical administration of prostaglandin synthetase inhibitors in the treatment of non-infectious inflammatory diseases.