The prevalence of hypertension is higher among blacks than whites. However, inconsistent findings have been reported on the incidence of hypertension among middle-aged and older blacks and whites, and limited data are available on the incidence of hypertension among Hispanics and Asians in the United States. Therefore, this study investigated the age-specific incidence of hypertension by ethnicity for 3146 participants from the Multi-Ethnic Study of Atherosclerosis. Participants, age 45 to 84 years at baseline, were followed for a median of 4.8 years for incident hypertension, defined as systolic blood pressure 140 mm Hg, diastolic blood pressure 90 mm Hg, or the initiation of antihypertensive medications. The crude incidence rate of hypertension, per 1000 person-years, was 56.8 for whites, 84.9 for blacks, 65.7 for Hispanics, and 52.2 for Chinese. After adjustment for age, sex, and study site, the incidence rate ratio (IRR) for hypertension was increased for blacks age 45 to 54 (IRR: 2.05 [95%CI: 1.47 to 2.85]), 55 to 64 (IRR: 1.63 [95% CI: 1.20 to 2.23]), and 65 to 74 years (IRR: 1.67 [95% CI: 1.21 to 2.30]) compared with whites but not for those 75 to 84 years of age (IRR: 0.97 [95% CI: 0.56 to 1.66]). Additional adjustment for health characteristics attenuated these associations. Hispanic participants also had a higher incidence of hypertension compared with whites; however, hypertension incidence did not differ for Chinese and white participants. In summary, hypertension incidence was higher for blacks compared with whites between 45 and 74 years of age but not after age 75 years. Public health prevention programs tailored to middle-aged and older adults are needed to eliminate ethnic disparities in incident hypertension. © 2011 American Heart Association, Inc.