The aim of the study was to compare the efficacy of travoprost 0.004% eye drops added to therapy with timolol 0.5%. The study included 40 patients (80 eyes) with open angle glaucoma and intraocular pressure (IOP) above 18 mm Hg treated with topical beta blocker (timolol 0.50% twice a day). Travoprost 0.004% was added to timolol 0.5% therapy once daily in the evening. Follow up examinations were scheduled at 7 days, one month and three months. IOP lowering was achieved in all patients. Substantial lowering of 2.42 mm Hg was achieved after the first week of treatment. Further lowering and stabilization of IOP was recorded at three months, with total IOP decrease of 3.97 mm Hg; the difference was statistically significant (chi2=6.7743; p<0.01). At three months, target IOP was recorded in 64 eyes (16.4+/-0.7 mm Hg) and failed to be achieved in 16 eyes (21.1+/-2.3 mm Hg). Mild hyperemia was found in two patients and discrete hyperemia in 26 patients. Burning sensation associated with the use of travoprost 0.004% eye drops was reported by 68 patients. In conclusion, the use of travoprost 0.004% eye drops resulted in successful lowering of IOP and achievement of target IOP.