Multiple studies have shown that the carotid artery intima-media thickness (IMT), as measured noninvasively by ultrasonography, is directly associated with an increased risk of cardiovascular disease. Because it has been shown to be an independent predictor of cardiovascular disease after adjustment for traditional risk factors, it is the only noninvasive imaging test currently recommended by the American Heart Association for inclusion in the evaluation of risk. However, it remains unclear how much additional information beyond that afforded by traditional risk factors is gained by inclusion of IMT in risk profiles. Change in IMT is increasingly being used as the end point in interventional trials. Meaningful differences in progression rates have been shown in progression rates in trials of either lipid-lowering drugs or calcium channel blockers involving several hundred subjects over a period of several years. Acceptance of a standardized protocol for measuring IMT change would facilitate comparison of results from the many trials using this technique. However, uncertainty about which measure of IMT offers the best end point has inhibited methodologic standardization.