Introduction. This study was aimed at evaluating the safety and efficacy of brinzolamide 1% suspension (Azopt® 1%) and travoprost 0.004% (Travatan®) combined therapy in patients with open-angle glaucoma or ocular hypertension who are in need of additional intraocular pressure lowering. Material and methods. This is a prospective, three-month, open-label, clinical study. Forty patients (80 eyes) with primary open-angle glaucoma or ocular hypertension on Travatan® treatment and with unsatis-factory results in lowering intraocular pressure were included in the study. The qualifying intraocular pressure on previous treatment with Travatan® (at least 6 weeks) was 22-36 mmHg in at least one eye at 8 a.m. intraocular pressure measurements at three eligibility visits. The patients received brinzolamide 1% twice a day in addition to travoprost 0.004% given once a day in the evening for 3 months. The follow-up examinations assessing the safety and efficacy of combined therapy of brinzolamide 1% and travoprost 0.004% were performed after 1 and 3 months. Results. Adjunctive therapy with brinzolamide resulted in statistically significant reductions in intraocular pressure from the travoprost baseline at all visits. Treatment with brinzolamide/travoprost caused statistically significant sustained reduction in intraocular pressure with the reduction of 17.39% (p<0.001) after 4 weeks and 20.08% (p<0.001) after 12 weeks. The intraocular pressure change from the baseline ranged from -3.9 mmHg after 4 weeks to -4.48 mmHg after 12 weeks. The most frequently related adverse effect was abnormal taste and blurred vision. Conclusion. Brinzolamide 1% (b.i.d.) used adjunctively with travoprost 0.004% (q.d.) lowers intraocular pressure significantly compared to travoprost alone. Both drugs were well tolerated and safe in the studied patients.