Abstract Purpose of Review To review the current evidence on research related to age of hypertension onset—its definition, correlates, heritability, and association with adverse outcomes. We also propose a framework for implementing assessment of hypertension onset age into clinical practice. Recent Findings Prior studies have used both objective measurements and self-report to determine age of hypertension onset or early-onset hypertension. Yet, no criterion for standard definition currently exists for either. Data from epidemiological and clinical studies demonstrate that early-onset hypertension is a highly heritable trait that confers an increased risk for cardiovascular death and end-organ damage compared with late-onset hypertension. Summary Literature to date suggests that (parental) age of hypertension onset can be feasibly assessed for estimating (1) risk of future hypertension in non-hypertensive persons; and (2) the propensity for cardiovascular disease in individuals with established hypertension.