OBJECTIVE Fixed combinations of 0.2% brimonidine-0.5% timolol and 2% dorzolamide-0.5% timolol are used to lower intraocular pressure (IOP). The objective of this study was to evaluate the IOP-lowering efficacy and ocular tolerability of brimonidine-timolol compared with dorzolamide-timolol when used as monotherapy or as adjunctive therapy to a prostaglandin analog (PGA) in patients with glaucoma or ocular hypertension. METHODS Pooled data analysis of two randomized, investigator-masked, 3-month, parallel-group studies with identical protocols (ten sites). In all, 180 patients with open-angle glaucoma or ocular hypertension who were in need of lower IOP received topical brimonidine-timolol BID or dorzolamide-timolol BID as monotherapy (n = 101) or as adjunctive therapy to a PGA (latanoprost, bimatoprost, or travoprost) (n = 79). BACKGROUND The studies are registered with the identifiers NCT00822081 and NCT00822055 at http://www.clinicaltrials.gov. METHODS IOP was measured at 10 a.m. (peak effect) at baseline and at months 1 and 3. Tolerability/comfort was evaluated using a patient questionnaire. RESULTS There were no statistically significant between-group differences in patient demographics. Most patients were Caucasian, and the mean age was 68 years. There were also no statistically significant differences between treatment groups in baseline IOP. At month 3, the mean (SD) reduction from baseline IOP for patients on fixed-combination monotherapy was 7.7 (4.2) mmHg (32.3%) with brimonidine-timolol versus 6.7 (5.0) mmHg (26.1%) with dorzolamide-timolol (p = 0.040). The mean reduction from PGA-treated baseline IOP for patients on fixed-combination adjunctive therapy was 6.9 (4.8) mmHg (29.3%) with brimonidine-timolol versus 5.2 (3.7) mmHg (23.5%) with dorzolamide-timolol (p = 0.213). Patients on brimonidine-timolol reported less burning (p < 0.001), stinging (p < 0.001), and unusual taste (p < 0.001) than patients on dorzolamide-timolol. CONCLUSIONS Fixed-combination brimonidine-timolol provided the same or greater IOP lowering compared with fixed-combination dorzolamide-timolol. Both fixed-combination medications were safe and well-tolerated. Brimonidine-timolol received higher ratings of ocular comfort than dorzolamide-timolol. The duration of the studies was 3 months, and additional studies will be needed to compare the efficacy and tolerability of brimonidine-timolol and dorzolamide-timolol during long-term treatment.