BACKGROUND: Angiotensinogen is the proximal precursor of the angiotensin peptide hormones of the renin-angiotensin-aldosterone system (RAAS). Clinical trials are ongoing targeting angiotensinogen for the treatment of hypertension and heart failure. The epidemiology of angiotensinogen is not well defined, particularly its relationship to ethnicity, sex, and blood pressure (BP)/hypertension. OBJECTIVES: The authors sought to determine the relationship of circulating angiotensinogen levels to ethnicity, sex, BP, incident hypertension, and prevalent hypertension in a modern sex-balanced ethnically diverse cohort. METHODS: Plasma angiotensinogen levels were measured in 5,786 participants from the MESA (Multi-Ethnic Study of Atherosclerosis). Linear, logistic, and Cox proportional hazards models were utilized to examine the associations of angiotensinogen with BP, prevalent hypertension, and incident hypertension, respectively. RESULTS: Angiotensinogen levels were significantly higher in females than males and differed across self-reported ethnicities with the ordering (from highest to lowest): White, Black, Hispanic, and Chinese adults. Higher levels were associated with higher BP and odds of prevalent hypertension, after adjusting for other risk factors. Equivalent relative differences in angiotensinogen were associated with greater differences in BP in males vs females. In males not taking RAAS-blocking medications, a standard deviation increment in log-angiotensinogen was associated with 2.61 mm Hg higher systolic BP (95% CI: 1.49-3.80), while in females the same increment in angiotensinogen was associated with 0.97 mm Hg higher systolic BP (95% CI: 0.30-1.65). CONCLUSIONS: Significant differences in angiotensinogen levels are present between sexes and ethnicities. A positive association is present between levels and prevalent hypertension and BP, which differs between sexes.