Background Travoprost has been widely used for the treatment of patients with open-angle glaucoma (OAG) or ocular hypertension (OH). The aim of this study was to evaluate the intraocular pressure (IOP) lowering efficacy of travoprost 0.004% monotherapy in patients previously treated with other topical hypotensive medications, and in previously untreated patients.Methods This open-label, 12-week study in 1651 adult patients with ocular hypertension or open-angle glaucoma who were untreated or required a change in therapy (due to either inadequate efficacy or safety issues) as judged by the investigator was conducted at 6 sites in China. Previously treated patients were instructed to discontinue their prior medications at the first visit. All the patients were dosed with travoprost 0.004% once-daily at 8 p.m. In both eyes for 12 weeks. Efficacy and safety evaluations were conducted at week 4 and 12. IOP measurements were performed at the same time of day at the follow-up visits.Results For patients transitioned to travoprost, mean IOP reductions from baseline in untreated and treated patients with different prior medications at week 12 were: latanoprost, (4.3±4.6) mmHg; β-blocker, (6.3±4.0) mmHg; a-agonist, (7.5±4.3) mmHg; topical carbonic anhydrase inhibitors, (8.0±4.9) mmHg. All mean IOP changes from baseline were statistically significant (P