OBJECTIVE: To describe the relationship of blood pressure (BP), antihypertensive medication use, and other factors to serial measurements of retinal arteriolar diameters over time in the Beaver Dam Eye Study. METHODS: Retinal arteriolar diameter was measured by computer-assisted methods and summarized as central retinal arteriolar equivalent (CRAE) in 4573 persons aged 43 to 99 years at 4 examinations (each separated by 5 years) during a 15-year period. Associations of CRAE with risk factors measured concurrently and 5 years previously were determined using multivariate analyses. RESULTS: While adjusting for image quality, refraction, and lens status, age (per 10 years: β estimate, -0.73; P < .001), systolic BP (per 10 mm Hg: concurrent examination, -2.74; P < .001; previous examination, -1.75; P < .001), smoking status (smoker vs nonsmoker: concurrent examination, 4.29; P < .001; previous examination, 1.63; P = .004), body mass index (per category: concurrent examination, -0.51; P = .05; previous examination, -0.22; P = .44), and heavy alcohol consumption (drinking) (current vs past/never heavy drinker: concurrent examination, -2.54; P = .03; previous examination, -2.42; P = .02) were associated with CRAE. In the same model, there were significant interactions between concurrent and previous systolic BP (0.11; P = .003) and between concurrent and previous body mass index (0.12; P = .04). Use of calcium channel blockers at both the concurrent and past examination (vs neither examination, 1.59; P = .01), but not other classes of antihypertensive drugs, was associated with CRAE. CONCLUSIONS: Retinal arteriolar diameter is independently associated with past and current systolic BP, calcium channel blocker use, smoking status, body mass index, and heavy drinking during 5-year intervals. The relationships with CRAE are stronger for concurrent than for past measures of these variables.