Our aim is to study associations between circulating endostatin, hypertension duration, and hypertensive target-organ damage. Long-term hypertension induces cardiovascular and renal remodeling. Circulating endostatin, a biologically active derivate of collagen XVIII, has been suggested to be a relevant marker for extracellular matrix turnover and remodeling in various diseases. However, the role of endostatin in hypertension and hypertensive target-organ damage is unclear. Serum endostatin was measured in 2 independent community-based cohorts: the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS; women 51%; n=812; mean age, 75 years) and the Uppsala Longitudinal Study of Adult Men (ULSAM; n=785; mean age, 77.6 years). Retrospective data on blood pressure measurements and antihypertensive medication (PIVUS >5 years, ULSAM >27 years), and cross-sectional data on echocardiographic left ventricular mass, endothelial function (endothelium-dependent vasodilation assessed by the invasive forearm model), and urinary albumin/creatinine ratio were available. In PIVUS, participants with ≥5 years of history of hypertension portrayed 0.42 SD (95% confidence interval, 0.23-0.61; P<0.001) higher serum endostatin, compared with that of normotensives. This association was replicated in ULSAM, in which participants with 27 years hypertension duration had the highest endostatin (0.57 SD higher; 95% confidence interval, 0.35-0.80; P<0.001). In addition, higher endostatin was associated with higher left ventricular mass, worsened endothelial function, and higher urinary albumin/creatinine ratio (P<0.03 for all) in participants with prevalent hypertension. Circulating endostatin is associated with the duration of hypertension, and vascular, myocardial, and renal indices of hypertensive target-organ damage. Further studies are warranted to assess the prognostic role of endostatin in individuals with hypertension.