The MESA is a longitudinal study supported by the National Heart, Lung, and Blood Institute (NHLBI); its goal is identifying risk factors for subclinical atherosclerosis. Details of the study design have been published elsewhere (33). Between July 2000 and August 2002, 6814 men and women 45 to 84 years of age who identified themselves as white, black, Hispanic, or Chinese and were free of clinically apparent cardiovascular disease were recruited from 6 U.S. communities: Baltimore City and Baltimore County, Maryland; Chicago, Illinois; Forsyth County, North Carolina; Los Angeles County, California; Northern Manhattan and the Bronx, New York; and St. Paul, Minnesota. Each field site recruited participants from locally available sources, which included lists of residents, lists of dwellings, and telephone exchanges. In the last few months of the recruitment period, supplemental sources, such as lists of Medicare beneficiaries from the Centers for Medicare & Medicaid Services and referrals by participants, were used to ensure adequate numbers of minority and elderly participants. The age distribution of the final sample was as follows: 45 to 54 years (27%), 55 to 64 years (28%), 65 to 74 years (30%), and 75 years or older (16%). Percentages do not sum to 100 because of rounding. Coronary calcium was assessed by using chest computed tomography (CT) with a cardiac-gated electron-beam CT scanner (34) (Chicago, Los Angeles, and New York field centers) or a multidetector CT system (35) (Baltimore, Forsyth County, and St. Paul field centers) (36). All participants had scanning over phantoms of known physical calcium concentration. A cardiologist read all scans at the Harbor-UCLA Research and Education Institute in Torrance, California, to identify and quantify coronary calcification, calibrated according to the readings of the calcium phantom. Scans were read blindly with respect to scan pairs and to other participant data by using a computerized interactive scoring system similar to that described by Yaghoubi and colleagues (37). The score of Agatston and colleagues (38) was used in all analyses. The Agatston score and the volumetric calcium score were very highly correlated in this sample (r = 0.99). The presence of calcification was defined as an average Agatston score greater than 0.