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Background Although cerebral lesions ≥3mm on imaging are associated with incident stroke, lesions < 3mm are typically ignored. Objective To examine stroke risks associated with subclinical brain lesions by size (< 3 mm only, lesions ≥3 mm only, both < 3 mm and ≥3 mm) and white matter hyperintensities (WMH). Design Community cohort, Atherosclerosis Risk in Communities (ARIC) Study Setting Two ARIC sites with magnetic resonance imaging (MRI) data (1993–95) Participants 1,884 (99%) adults (50–73 years, 40% men; 50% black) with MRI and no prior stroke; average 14.5 years follow-up. Measurements MRI lesions: none (n=1611), < 3 mm only (n=50), ≥3 mm only (n=185), or both < 3 and ≥3 mm lesions (n=35); WMH score (0–9 scale). Outcomes: incident stroke (n=157), overall mortality (n=576), stroke mortality (n=50). Hazard Ratios (HR) estimated with proportional hazards models. Results Compared to no lesions, stroke risk was tripled with lesions < 3mm only (HR=3.47, 95% CI:1.86-6.49), doubled with lesions ≥3 mm only (HR=1.94, 95% CI:1.22-3.07), and was 8-fold higher with both < 3 mm and ≥3 mm-sized lesions (HR=8.59, 95% CI:4.69-15.73). Stroke risk doubled with WMH ≥3 (HR=2.14, 95% CI:1.45-3.16). Stroke mortality risk tripled with lesions < 3 mm only (HR=3.05, 95% CI:1.04-8.94), doubled with lesions ≥3 mm (HR=1.9, 95% CI:1.48-2.44) and was seven-times higher with both lesion sizes (HR=6.97, 95% CI:2.03-23.93). Limitations Few stroke events (n=147), especially hemorrhagic (n=15); limited numbers of participants with only lesions ≤3mm (n=50) or with both lesions ≤3mm and 3–20mm (n=35). Conclusions Very small cerebrovascular lesions may be associated with increased risks of stroke and mortality; having both < 3 mm and ≥3 mm lesions may represent a particularly striking risk increase. Larger studies are needed to confirm findings and provide more precise estimates.