AIMS: To evaluate efficacy and safety in patients with ocular hypertension or open angle glaucoma changed to latanoprost/timolol fixed combination (LTFC). METHODS: A prospective, multicentre, historical control in which qualified patients had their previous therapy substituted by LTFC and were followed for at least 2 months. RESULTS: In 1676 patients LTFC was continued in 93% throughout the observation period. In all patients LTFC reduced the intraocular pressure (IOP) from 20.6 (SD 3.8) to 17.7 (3.0) mm Hg (p<0.001) compared to previous monotherapies including latanoprost, timolol, alpha agonists or carbonic anhydrase inhibitors (CAI). LTFC provided more efficacy after changing from adjunctive therapies including: a beta blocker added to either CAI, alpha agonist, or pilocarpine, or CAI added to an alpha agonist, or latanoprost added to either CAI, alpha agonist, or beta blocker (unfixed combination), and travoprost added to timolol (p<0.007). LTFC was as effective as latanoprost used with dorzolamide/timolol fixed combination (-0.9 mm Hg, p = 0.1792). The most common reason to discontinue therapy was lack of efficacy (n = 70, 4%) and adverse event (n = 17, 1%). CONCLUSION: In a clinical setting, patients who have their monotherapy or adjunctive therapy substituted with LTFC may experience reduced IOP, good tolerability, and continuation of therapy for the first 2-3 months of treatment.