Effects of pharmacologic agents on experimental ocular inflammation induced by reverse passive Arthus reactions were investigated by a slit-lamp technique utilizing fluorescein-labeled rabbet serum albumin as an indicator. Cobra venom factor completely eliminated inflammatory responses, indicating that the complement system is a trigger for this type of ocular inflammation. Antihistamines mainly suppressed the early vascular response. Reserpine and indomethacin remarkably inhibited the increase of the permeability of the blood-aqueous barrier over the first 5 hr. Epinephrine and steroid hormone were also effective. Neither diethylcarbamazine nor isonicotinic acid showed effects on the permeability changes induced in this type of inflammation.