The study represent an up-to-date of the role and place of alpha 2-adrenergic agonists in glaucoma treatment. The first available alpha 2-agonist, clonidine is of historical importance today. Apraclonidine decrease the aqueous humor secretion and episcleral venous pressure. It is employed to prevent or blunt the acute intraocular pressure rise after ocular laser therapy. It is not recommended as long term therapy due to its high incidence of local adverse reactions and tachyphylaxis. Brimonidine became the alpha 2-agonist of choice in glaucoma chronic treatment, acting by decreasing aqueous humor secretion and increasing uveoscleral outflow. It has a lower incidence of the ocular adverse effects because of greater alpha 2 selectivity. Brimonidine has neuroprotective effect, which is an important feature in the new contexts of glaucoma pathogenesis. Brimonidine has hypotensor effect similar with timolol but with a greater incidence of adverse local reactions. It has been no effects on cardiopulmonary function. Brimonidine would be of value as first-line therapy in patients who have contraindications to beta-blockers.