We evaluated the effectiveness of topical apraclonidine (ALO 2145, p-amino clonidine hydrochloride) in suppressing an acute postoperative intraocular pressure (IOP) rise following Nd:YAG laser iridotomy. Fifty-eight eyes (45 patients) with chronic primary angle-closure glaucoma underwent Q-switched Nd:YAG laser iridotomy. Twenty-nine eyes followed prospectively underwent Nd:YAG laser iridotomy following the topical administration of 0.5% apraclonidine prior to and immediately following the procedure. A retrospective control group of 29 eyes underwent Nd:YAG laser iridotomy without topical apraclonidine. Only one eye (3.4%) treated with apraclonidine experienced an IOP rise greater than 10 mm Hg over baseline, while five among 29 untreated eyes (17.2%) developed an IOP rise greater than 10 mm Hg.