Purpose: Ocular blood flow dysregulation has been implicated in the pathogenesis of glaucoma. Whereas the effect of single antiglaucoma substances on ocular blood flow has been addressed in various experiments, evidence for fixed combinations is sparse. In the present study, we set out to compare the effects of latanoprost 0.005%/timolol 0.5% (LT) fixed combination and brimonidine 0.2%/timolol 0.5% (BT) fixed combination on intraocular pressure (IOP) and ocular blood flow. Methods: In the present study, which followed a randomized, double-masked 2-way crossover design, 16 patients with primary open-angle glaucoma and 2 patients with ocular hypertension were included. The patients underwent a 6-week treatment with LT and a 6-week treatment with BT after a washout for previous antiglaucoma medication. Optic nerve head blood flow (ONHBF) was measured using laser Doppler flowmetry; retrobulbar flow velocities were measured using color Doppler imaging in the ophthalmic artery, the central retinal artery, and the posterior ciliary arteries. IOP was measured at 8 AM, 12 PM, and 4 PM. Results: The mean baseline IOP was 25.3 +/- 2.8 mmHg. Both drugs were equally effective in reducing IOP (LT: -35.0% +/- 10.0%; BT: -33.6% +/- 8.8%, P = 0.463 between groups). In addition, no difference in ocular perfusion pressure was observed between the 2 treatment groups (P = 0.1, between groups). Neither LT nor BT altered ONHBF (P = 0.4, baseline vs. treatment) and no effect on flow velocities in the retrobulbar vessels was seen with either of the 2 treatments. Conclusions: In the present study, a 6-week treatment with LT or BT was equally effective in reducing IOP. In addition, none of the administered drugs induced a significant effect on ocular blood flow parameters.