Aqueous humor catecholamine levels were measured in 14 patients admitted to hospital for cataract or glaucoma surgery. Norepinephrine was detected in all patients. Epinephrine was detected in one patient who had received a preoperative retrobulbar injection of epinephrine. Dopamine was not detected in any patients. The highest level of norepinephrine was detected in cataract patients with normal intraocular pressures (mean = 7.18 nmol/l).