Seven cynomolgus monkeys underwent a histologically confirmed left superior cervical ganglionectomy (SCGx). Unilateral ocular sympathetic denervation persisting for at least 2 yr was confirmed by ipsilateral ptosis, miosis, supersensitivity of pupillary dilation to topical phenylephrine, and profound pupillary hyporesponsiveness to topical hydroxyamphetamine. Intraocular pressure 8-9 and 23-27 months postoperatively were identical in the denervated and contralateral control eyes. This model should facilitate studies of aqueous humor physiology and pharmacology.