Carotid intima-media thickness (CIMT) testing is recognized as a valid method for the noninvasive assessment of atherosclerosis. In addition to its association with known cardiovascular risk factors and both prevalent and incident coronary heart disease, the rate of CIMT progression is directly related to the risk for future cardiovascular events. Subsequently, CIMT has been a valuable research tool in clinical trials in the assessment of therapeutic agents directed against atherosclerosis. An overview of CIMT testing including its precise measurement, establishment as a surrogate for atherosclerosis by epidemiologic trials, role in clinical trials, and potential applications in both primary and secondary coronary heart disease prevention is presented.