This study investigated the effect of betaxolol, a beta 1 selective blocker, on the retinal circulation in 10 patients with ocular hypertension. In a masked randomised fashion, one eye of each subject received betaxolol and the fellow eye received placebo (hypromellose). Retinal blood flow (RBF) was determined in a major temporal vein of each eye just prior to instillation of drops and 2 h later, using laser Doppler velocimetry and monochromatic fundus photography. There was an increase of 15.0% in RBF (p = 0.03) in the betaxolol-treated eyes. No significant change was observed in the placebo-treated eyes. Intraocular pressure was reduced by 27.7% in the treated eyes, resulting in an increase of 16.9% in perfusion pressure (p = 0.02) compared with an 8.4% increase in placebo-treated eyes (p = 0.15). This study demonstrated that betaxolol increases RBF in eyes with ocular hypertension; this increase is probably related to the increase in perfusion pressure.