To investigate the relationship between coronary heart disease risk factors and coronary artery calcification in middle age adults from the Muscatine Study. From 1992 through 1995, ultrafast computed tomography was used to measure coronary artery calcification. The study has been extended through January, 2001 in order to examine the role of electron beam computed tomography in detecting the presence and quantity of coronary artery calcification, a marker of the atherosclerotic process.