The effect on contralateral eyes after injuries to 1 eye is called the consensual reaction and is postulated to be either the consequence of a neural reflex or one achieved by circulating substances. Trigeminal stimulation always caused ipsilateral miosis, ocular hyperemia, intraocular hypertension and a disruption of the blood-aqueous barrier. Disruption of the blood-aqueous barrier in the contralateral eye after stimulation of the trigeminal nerve always occurred and depended on intact sensory innervation to that globe in rabbits. The disruption was not prevented by pretreatment of the animals with indomethacin. The phenomenon of disruption of the barrier was sometimes accompanied by an elevation of intraocular pressure in the contralateral eye but not by the other irritative responses. Thus, unilateral stimulation of a sensory nerve, the trigeminal, in the rabbit, can produce ipsilateral and contralateral disruption of the blood-aqueous barrier.