BACKGROUND: Prehypertension (blood pressure (BP) of 120-139mm Hg systolic and/or 80-89mm Hg diastolic) is highly prevalent and is associated with increased cardiovascular risk. Our goal was to investigate the extent to which prehypertension is associated with end-organ alterations in cardiac structure and function in a large biracial cohort of older men and women. METHODS: We studied 4,871 participants of the Atherosclerosis Risk in Communities (ARIC) study who attended visit 5 (2011-2013) and underwent two-dimensional echocardiography while free of prevalent coronary heart disease or heart failure. We categorized participants into 3 groups: optimal BP (BP <120mm Hg and <80mm Hg) (n = 402), prehypertension (n = 537), and hypertension (n = 3,932). RESULTS: Individuals with prehypertension (75±5 years) had higher left ventricular (LV) mass index and wall thickness, and higher prevalence of abnormal LV geometry than those with optimal BP (74±5 years), but lower than those with frank hypertension (76±5 years). In addition, participants with prehypertension had impairment of diastolic parameters (E/A, E′ and E/E′), and had higher prevalence of mild and moderate-severe diastolic dysfunction compared to those with optimal BP, but no differences in systolic parameters. These differences in cardiac structure and function remained significant after adjusting for important clinical covariates. CONCLUSION: In the ARIC cohort at visit 5, prehypertension was associated with increased LV remodeling and impaired diastolic function, but not systolic function, suggesting that even mildly elevated BP within the normal range is associated with cardiac end-organ damage.