© American Journal of Hypertension, Ltd 2017. BACKGROUND Higher blood pressure during young adulthood may increase cardiovascular and kidney disease risk later in life. This study examined the association of cumulative systolic blood pressure (SBP) exposure during young adulthood through midlife with urine albumin-to-creatinine ratios (ACR) measured during midlife. METHODS We used data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, a biracial cohort recruited in 4 urban areas during years 1985-1986. Cumulative SBP was calculated as the average SBP between 2 exams multiplied by years between exams over 20 year years. ACR was measured 20 years after baseline when participants were age 43-50 years (midlife). A generalized additive model was used to examine the association of log ACR as a function of cumulative SBP with adjustment for covariates including SBP measured concurrently with ACR. RESULTS Cumulative SBP ranged from a low of 1,671 to a high of 3,260 mm Hg. Participants in the highest cumulative SBP quartile were more likely to be male (61.4% vs. 20.7%; P < 0.001), Black (61.5% vs. 25.6%; P < 0.001) and have elevated ACR (18.7% vs. 4.8%; P < 0.001) vs. lowest quartile. Spline regression curves of ACR vs. cumulative SBP demonstrated an inflection point in ACR with cumulative SBP levels >2,350 mm Hg with linear increases in ACR above this threshold. Adjusted geometric mean ACR values were significantly higher with cumulative SBP ≥2,500 vs. <2500 (9.18 [1.06] vs. 6.92 [1.02]; P < 0.0001). CONCLUSION Higher SBP during young adulthood through midlife is associated with higher ACR during midlife.