OBJECTIVE To compare hypotensive effect of latanoprost versus timolol-dorzolamide association on patients with glaucoma. METHODS We studied 102 eyes in 52 patients with intraocular pressure (IOP) higher than 21 mmHg, previously treated with a betablocker. Patients were divided in two groups. Treatment was changed on group 1 (51 eyes in 27 patients) to a timolol-dorzolamide association. Group 2 (51 eyes in 27 patients) changed treatment to latanoprost. After determination of previous IOP, readings were taken at 1, 3 and 8 months later. RESULTS Both groups showed a decrease in IOP levels: Group 1, 5.6 mmHg and Group 2, 8.5 mmHg. Association between timolol and dorzolamide reached the highest hypotensive effect after the first month of treatment and remained constant during the rest of the study period. Latanoprost showed a maximal effect after the third month of treatment and maintained its effect all through the study as well. Latanoprost behaved similar to associated timolol-dorzolamide not showing significant differences during the first month of treatment. Significant differences appeared at third and eighth month favoring latanoprost (p<0.005 and p<0.001 respectively). CONCLUSIONS There was a similarity in efficacy of both treatments. However, after the third month latanoprost became more effective than the timolol-dorzolamide association.