Clonidine, in the enucleated arterially perfused cat eye, was found to produce a decrease in the rate of aqueous humor production. The mechanism of action for this response has been ascribed to a vasoconstriction of afferent ciliary process blood vessels to decrease ultrafiltration. Cold, as a stimulus to the cornea, was found to produce an easily reversible decrease in aqueous humor production. The mode of action of this response is being studied. Changes of intraocular pressure, arterial pressure or of osmotic pressure induced no local intraocular reflexes which influenced aqueous humor production. BIBLIOGRAPHIC REFERENCES: Macri, F.J. and Cevario, S.J.: Blockade of the ocular effects of acetazolamide by phencyclidine. Exp. Eye Res. 24: 121-127, 1977.