Two concentrations of levobunolol (0.5% and 1%) and one concentration of timolol (0.5%) were evaluated for the control of elevated intraocular pressure (IOP) in a double-masked, randomized study. Fifty-one patients received one of the three study treatments in both eyes bid for one year. Both drugs were equally effective in reducing IOP: The overall reduction in mean IOP was slightly more than 9 mm Hg in all three treatment groups. Levobunolol was as safe and effective as timolol for the long-term control of elevated IOP.