Timolol, a relatively new .beta.-adrenergic blocker found to lower intraocular pressure in man, was not observed to have any side effects upon the visual system. This study utilized pupillography to determine the effect of conjunctival instillation of 0.5% timolol ophthalmic solution upon pupillary size and reaction. No clinically significant effect was observed, but a statistically significant decrease in the amplitude of redilation of the pupil was found in the eye that received timolol.