OBJECTIVE To compare ocular blood flow in untreated primary open-angle glaucoma and ocular hypertension using scanning laser Doppler flowmetry and pulsatile ocular blood flow. METHODS Fourteen ocular hypertensive subjects and 10 patients with primary open-angle glaucoma were matched for intraocular pressure, mean arterial blood pressure, and age. They had scanning laser Doppler flowmetry images taken centered on the optic disk. Pulsatile ocular blood flow readings were performed in sitting, standing, and supine positions. No subjects were receiving topical antiglaucoma treatment, systemic beta-blockers, calcium antagonists, or nitrates at the time of measurement. RESULTS Laser Doppler flowmetry results showed a significant reduction in blood velocity, volume, and flow at the lamina cribrosa and the temporal neuroretinal rim in glaucoma compared to ocular hypertension (P < .05). No difference was found between the groups at the nasal neuroretinal rim or the nasal juxtapapillary retina. There was a significant increase in minimum velocity (P = .03) at the temporal juxtapapillary retina in glaucoma compared to ocular hypertension. The ocular pulse amplitude, pulse volume, and pulsatile ocular blood flow were significantly lower (P < .05) in the glaucoma group compared to ocular hypertension in sitting and standing positions. CONCLUSIONS Having controlled for factors known to affect perfusion pressure, we found evidence of reduced ocular blood flow in primary open-angle glaucoma compared with ocular hypertension. Our findings indicate a reduction in choroidal and short posterior ciliary artery circulation in primary open-angle glaucoma. Whether these changes in blood flow are a cause or a consequence of glaucomatous optic atrophy is still unknown.