PURPOSE: To compare the efficacy and tolerability of fixed-combination latanoprost and timolol applied in the evening with the concomitant use of the individual components. Design: Twelve-week, randomized, double-masked, multicenter study. Participants: Five hundred seventeen randomized patients with ocular hypertension; open-angle, pigmentary, or exfoliation glaucoma; and baseline (after washout) intraocular pressure (IOP) levels between 23 and 33 mmHg. Methods: Patients received either the fixed combination of latanoprost and timolol once daily in the evening and a placebo in the morning and evening or the unfixed combination of latanoprost once daily in the evening and timolol in the morning and evening. Study visits were at weeks 2, 6, and 12. Main Outcome Measures: The primary efficacy end point was mean change from baseline to week 12 in diurnal IOP (mean IOPs of 8 am, 12 pm, and 4 pm). The fixed combination was considered noninferior to the unfixed combination if the upper limit of the 95%confidence interval (CI) of the difference was <1.5 mmHg (analysis of covariance). Adverse events were recorded at each visit. Results: In all, 502 patients were included in intent-to-treat analyses (fixed combination, n=255; unfixed combination, n=247). For the fixed-and unfixed-combination groups, mean baseline diurnal IOP levels were 25.4 mmHg and 25.2 mmHg, respectively, and mean diurnal IOP reductions were 8.7mmHg and 9.0 mmHg (between-treatment difference, 0.3mmHg; 95%CI,-0.1 to 0.7 mmHg; P=0.15). Both treatments were well tolerated. Conclusions: The fixed combination of latanoprost and timolol administered once daily in the evening is not inferior to the unfixed combination of latanoprost once daily in the evening and timolol twice daily. The fixed combination provides an effective and well-tolerated alternative to multiple instillations. PURPOSE: To compare the efficacy and tolerability of fixed-combination latanoprost and timolol applied in the evening with the concomitant use of the individual components. Design: Twelve-week, randomized, double-masked, multicenter study. Participants: Five hundred seventeen randomized patients with ocular hypertension; open-angle, pigmentary, or exfoliation glaucoma; and baseline (after washout) intraocular pressure (IOP) levels between 23 and 33 mmHg. Methods: Patients received either the fixed combination of latanoprost and timolol once daily in the evening and a placebo in the morning and evening or the unfixed combination of latanoprost once daily in the evening and timolol in the morning and evening. Study visits were at weeks 2, 6, and 12. Main Outcome Measures: The primary efficacy end point was mean change from baseline to week 12 in diurnal IOP (mean IOPs of 8 am, 12 pm, and 4 pm). The fixed combination was considered noninferior to the unfixed combination if the upper limit of the 95% confidence interval (CI) of the difference was <1.5 mmHg (analysis of covariance). Adverse events were recorded at each visit. Results: In all, 502 patients were included in intent- n = 255; unfixed combination, n = 247). For the fixed-and unfixed-combination groups, mean baseline diurnal IOP levels were 25.4 mmHg and 25.2 mmHg, respectively, and mean diurnal IOP reductions were 8.7 mmHg and 9.0 mmHg (between- Conclusions: The fixed combination of latanoprost and timolol administered once daily in the evening is not inferior to the unfixed combination of latanoprost once daily in the evening and timolol twice daily. The fixed combination provides an effective and well-tolerated alternative to multiple instillations.