OBJECTIVE： To confirm the efficacy and safety of latanoprost in treating glaucoma.METHODS： In a double blind， randomized control clinical trial， we compared the efficacy and adverse drug reactions of once daily topically applied 0.005％ latanoprost with those of twice daily 0.5％ timolol for 12 weeks in patients with open angle glaucoma or ocular hypertension.RESULTS： The study included 46 patients（22 pts.randomized to latanoprost treatment， 24 pts.to timolol） ， 46 patients remained at the end of the study.Comparing with baseline diurnal intraocular pressure（IOP） ， the IOP reduction（mean±standard deviation） achieved with latanoprost（7.86±2.39） mmHg， （31.1％， P<0.001），and timolol（6.24±2.58）mmHg （24.9%，P<0.001），the difference between the two groups（1.62mmHg） being significant（P<0.01）. Two patients treated with latanoprost had foreign body sensation. No other ocular and systemic adverse reactions related to the two drugs were found. CONCLUSION: The results of this study demonstrated that 0.005% latanoprost applied once daily is well tolerated and more effective in reducing IOP than 0.5% timolol applied twice daily. Thus, latanoprost has the potential for becoming one of the ideal antiglaucoma drugs.