Effect and side effects of adding 0.2% brimonidine to beta blockers was studied in 44 eyes of 32 glaucoma patients with inadequately controlled intraocular pressure(IOP) with beta blockers alone. Routine eye examination and IOP measurement were performed before the additive therapy. 0.2% brimonidine eye drops were topically applied three times a day with previously used beta blockers. IOP was measured at 1 week, 1 month, and 3 months after the combined therapy. Mean IOP was 17.2±1 . 8㎜Hg before combined therapy ; 13.5±1 . 6㎜Hg after 1 week, 14.3±2 . 5㎜Hg after 1 month and 13.6±2 . 3㎜Hg after 3 months of therapy. Side effects of combined therapy were oral dryness(25.0%), ocular pain(9.4%), and blurring(6.3%). These results indicate that adding 0.2% brimonidine in patients treated with beta blockers causes a further reduction of IOP that may prove to be clinically useful in glaucoma therapy(J Korean Ophthalmol Soc 41:731~736, 2000)