PURPOSE: To study the influence of different medications on retinal vessel diameters. DESIGN: Cross-sectional study. METHODS: Retinal photographs in the Beaver Dam Eye Study (n = 4926, aged 43 to 84 years) were digitized, and the diameters of retinal vessels were measured. Participants' current medications were recorded at the examination. RESULTS: There were few significant associations between medication use and retinal vessel diameters. After adjusting for age, blood pressure, and other factors, participants who were using topical beta-blocker eyedrops had narrower retinal arteriolar (P = .05) and venular (P = .006) diameters than nonusers. Systemic beta-blocker was not associated with retinal vessel diameter size. CONCLUSION: We found few associations between current medication use and retinal vessel diameter. Retinal vessels were narrowed in those taking antiglaucoma medications, most strikingly in those prescribed topical beta-blockers, although such a relationship could not be established among those using systemic beta-blockers.