Various interventions for cardiovascular disease (CVD) slow or reverse the progression of atherosclerosis and reduce the risk of clinical coronary events. Although the cardiovascular benefits of hormone replacement therapy have been demonstrated in observational studies in predominantly healthy women, no benefit has been found in a randomized clinical trial conducted in older women with established CVD. It is possible that the benefit of hormone therapy occurs when it is used relatively early in the progression of atherosclerosis. Techniques are now available to monitor the various stages of atherosclerosis. Quantitative coronary angiography, a technique used to evaluate relatively late-stage atherosclerosis, has been shown to predict the risk of subsequent clinical coronary events. B-mode ultrasonography of the intima-media wall thickness (IMT) of the carotid artery can assess the earlier stages of atherosclerosis and correlates with atherosclerosis risk factors, as well as with clinical cardiovascular and cerebrovascular outcome. This technique offers a relatively rapid and cost-effective method to test therapies for CVD and to screen for individuals who are at high risk for cardiovascular events. As an example of the use of atherosclerosis imaging to evaluate possible therapeutic interventions, measurements of IMT were performed in a randomized, controlled trial comparing oral 17β-estradiol with placebo. The results demonstrated that 17β-estradiol significantly reduces the progression of subclinical atherosclerosis in healthy, postmenopausal women when compared with placebo.