Timolol ophthalmic solution effectively reduced mean intraocular pressure (IOP) in Negro and Caucasian patients with chronic open angle glaucoma and untreated IOP of 22 mm Hg or higher. No differences in pressure lowering response were observed among the races although the Negroes required somewhat higher timolol concentrations to produce similar reductions from baseline IOP. Negro patients also appeared to have a more severe disease as indicated by the number of prior antiglaucoma drugs required and the untreated (baseline) pressures. An unexpected finding was the significantly greater number of Caucasians with dark irides who were discontinued from therapy because of inadequate pressure reduction.