•Every 12 hours 0.1% dipivefrin was administered to one eye and 2% epinephrine hydrochloride was administered to the fellow eye of 42 patients with primary open-angle glaucoma or ocular hypertension in a randomized, double-masked study lasting three months. Dipivefrin produced similar percent reductions in intraocular pressure (18.6%) to epinephrine (21.0%), as well as similar increases in outflow facility and pupil diameter. A significantly lower incidence of burning and stinging after drug instillation was noted with dipivefrin therapy. This study supported the contention that dipivefrin is an effective and safe alternative to epinephrine therapy for the reduction of elevated intraocular pressur