To evaluate control of intraocular pressure (IOP) and IOP fluctuation in patients with ocular hypertension or glaucoma treated with fixed-combination brimonidine–timolol compared with brimonidine or timolol monotherapy.Post hoc analysis of data from 2 identical, 12-month, randomized, double-masked, multicenter trials.Patients were treated bilaterally with fixed brimonidine–timolol twice a day (n = 385), brimonidine tartrate 0.2% 3 times a day (n = 382), or timolol 0.5% twice a day (n = 392). Diurnal IOP was measured at follow-up visits at weeks 2 and 6 and months 3, 6, 9, and 12. IOP fluctuation was defined as the standard deviation of IOP measurements.The percentage of patients with mean diurnal IOP <18 mm Hg and short-term (daily) IOP fluctuation ≤2 mm Hg was statistically significantly higher in the brimonidine–timolol group than in the brimonidine or timolol group at each follow-up visit (at month 12, brimonidine–timolol 43.0%; brimonidine 18.9%, timolol 33.5%, P ≤ .017). At each hour (8 AM, 10 AM, 3 PM, and 5 PM), the percentage of patients with mean IOP <18 mm Hg and long-term (intervisit) IOP fluctuation ≤2 mm Hg was statistically significantly higher with brimonidine–timolol than with brimonidine or timolol alone (at 8 AM, brimonidine–timolol 41.0%, brimonidine 11.3%, timolol 23.7%, P < .001).Patients treated with fixed-combination brimonidine–timolol were more likely than patients treated with either brimonidine or timolol alone to achieve a combination of low mean IOP and low short-term (daily) or long-term (intervisit) IOP fluctuation.