Purpose: To evaluate the relationship between retinal circulatory abnormalities and retinal nerve fiber layer (RNFL) thinning in early-stage open-angle glaucoma (OAG) to help elucidate the mechanisms underlying the development of glaucomatous optic neuropathy. Design: Prospective cross-sectional. Methods: Twelve patients with early OAG and a known maximum untreated intraocular pressure less than 22 mm Hg (age, 61.4 ± 9.7 years; Humphrey visual field mean deviation -2.7 ± 2.1) and eight age-matched healthy control subjects (age, 58.5 ± 8.3 years) were included in the study. Blood column diameter, centerline blood speed, and retinal blood flow were measured in the major inferior temporal retinal artery using a Canon laser Doppler blood flow instrument (CLBF 100; Canon, Tokyo, Japan). Peripapillary RNFL thickness was measured using a Stratus optical coherence tomography instrument. Results: On average, there were significant reductions in retinal blood speed (P = .009) and flow (P = .010) in OAG patients compared to controls. The RNFL was significantly thinner in the OAG patients compared to controls (P = .002). There were significant inverse correlations between retinal blood flow and average RNFL thickness and RNFL thickness in the inferior quadrant within the glaucoma group (Rsq = 0.50, P = .01; Rsq = 0.62, P = .003). Conclusion: The results showed that a thinner RNFL was associated with a higher retinal blood flow in patients with early-stage OAG. The mechanisms underlying this phenomenon remain to be elucidated.