Objectives: To describe the distribution of hypertension and its association with subclinical atherosclerosis in blacks and whites. Design: Population-based survey of 15 587 middle-aged adults from the Atherosclerosis Risk in Communities Study. Ultrasound-measured carotid artery intima media thickness (IMT) was used to estimate atherosclerosis. Hypertension was defined by the revised filth Joint National Committee categories. Continuous systolic and diastolic blood pressure measurements also were evaluated. Results: Among participants not reporting use of antihypertensive medication, 43% to 52% of black and 68% to 78% of white participants had optimal to high- normal blood pressure across the 4 study centers; 11% to 22% of black and 6% to 9% of white participants had stage I or higher hypertension. Use of antihypertensive medications was reported by 34% to 45% of blacks and 20% of whites; 11% to 17% of blacks had stage I or higher hypertension compared with 4% to 7% of whites when treated. Higher hypertension categories were associated with thicker intima medias in all ethnic and gender groups, in participants who did and did not use medications. In participants who did not use medications, multiple linear regression models adjusted for diastolic blood pressure and other risk factors found that systolic blood pressure was positively associated with IMT except in black men; diastolic blood pressure was not related to IMT in blacks and had a negative relation with IMT in white men and a J-shaped relation with IMT in white women. Results of similar direction and magnitude were found in participants who used medications. Conclusions: Hypertension was higher in blacks than whites and was associated with subclinical atherosclerosis. The association of atherosclerosis with hypertension is accounted for predominantly by systolic blood pressure. The intriguing negative association of diastolic blood pressure and atherosclerosis implies that pulse pressure may be an important correlate of atherosclerosis.