In a double-masked, randomized, controlled clinical trial, the authors evaluated the ocular hypotensive efficacy of twice-daily treatment with levobunolol (0.25 and 0.5%) and betaxolol (0.5%) in 85 patients with open-angle glaucoma or ocular hypertension. During the 3-month study, intraocular pressure (IOP) reductions in the two levobunolol groups were significantly greater than in the betaxolol group. From a mean baseline IOP of approximately 25 mmHg, overall mean reductions were 6.2 and 6.0 mmHg for the 0.25 and 0.5% levobunolol groups, respectively, and 3.7 mmHg for the betaxolol group. No clinically or statistically significant among-group differences were noted in the systemic safety variables evaluated. These data suggest that although all three treatments are effective, levobunolol provides a greater reduction in IOP than betaxolol.