Topically administered beta blockers are the preferred medical therapy for glaucoma. These agents reduce intraocular pressure (IOP), thereby preventing damage to the optic nerve and the subsequent loss of vision. Timolol, betaxolol, levobunolol, metipranolol, and carteolol are the topical beta blockers available in the U.S. They have similar IOP-lowering efficacy, but differ in other pharmacological properties. Topically administered beta blockers are generally well tolerated. They undergo systemic absorption, however, and can adversely affect cardiovascular and bronchopulmonary function in patients with existing diseases such as heart failure, sinus bradycardia, chronic obstructive airways disease, or asthma. Betaxolol, which is beta 1-selective, and carteolol, which has intrinsic sympathomimetic activity (ISA), may have systemic tolerability profiles superior to the traditional nonselective, non-ISA beta blockers. These hypotheses require confirmation in controlled clinical trials. Local adverse effects associated with beta blockers include stinging, burning, red eye, itching, tearing and loss of corneal sensitivity. Stinging upon instillation is a particularly frequent finding with betaxolol (up to 30% to 40% of patients). Preliminary evidence suggests that carteolol has the best local tolerability profile of these drugs.