© 2015 AUR. Rationale and Objectives: Vascular calcification independently predicts cardiovascular disease (CVD), and computed tomography (CT) is a useful tool to evaluate and quantify not only coronary but also thoracic aortic calcification (TAC). Previous TAC progression reports were limited to dialysis and renal transplant patients. This is the first study to evaluate TAC progression in a large multiethnic cohort without clinically evident CVD at entry. Methods: Non-contrast-enhanced cardiac CTs were obtained in 5886 of 6814 Multi-Ethnic Study of Atherosclerosis (MESA) participants (mean age, 62 years; 48% males; 40% white, 27% black, 21% Hispanic, and 12% Chinese). Baseline and follow-up TAC scores were derived. Results: Overall, 4308 (73%) participants had no detectable baseline TAC. Mean follow-up duration was 2.4 ± 0.8 years, during which 12% developed TAC. The overall incidence rate was 4.8%/year and was greater with age across gender and ethnic groups; TAC incidence was significantly lower in blacks than whites. After adjustment for follow-up duration, regression analyses showed age, systolic blood pressure, antihypertensives, and smoking were associated with incident TAC. A total of 1578 (27%) participants had TAC at baseline with a positive association between average annual TAC change and baseline age. Although the overall median change was 32.9 (-1.4 to 112.2) Agatston units, 27% showed an annual score change of ≥100 and blacks showed the lowest median across ethnic groups; 22.7 (-3 to 86.8). Age, systolic blood pressure, lipid-lowering medication, diabetes, and smoking were associated with TAC progression. Conclusions: In MESA, traditional CV risk factors were related to both TAC incidence and progression. Blacks had the lowest incidence and median change across ethnic groups, consistent with previous findings for coronary calcification.