The ability to follow changes in atherosclerotic plaque burden over time should provide an accurate measure of efficacy for different cardiovascular therapies. Coronary calcifications are associated with atherosclerotic coronary artery plaque, and the amount of coronary calcifications has been shown to correlate with the overall coronary plaque burden. The presence and extent of coronary calcifications can be assessed noninvasively by monitoring the progression of coronary calcification with electron beam tomography. With annual progression rates of 22% to 52% and a median interscan variability of only 5% to 8%, this technology provides an opportunity to monitor patients to assess the clinical efficacy of medical therapies in studies as short as 1 year. Several studies have demonstrated that the successful pharmacologic reduction of low-density lipoprotein cholesterol significantly mitigated the progression of the calcium score. Studies using serial computed tomographic scans indicate that the annual progression of coronary calcium varies between 30% and 50% in symptomatic or high-risk individuals and from 0% to 20% in patients treated effectively with lipid-lowering medication. An increased rate of progression of coronary calcium seems to indicate a substantially increased risk for adverse cardiac events, suggesting that this modality can be used to monitor the efficacy of therapy.