The Felodipine Atherosclerosis Prevention Study is designed to evaluate the efficacy of the calcium antagonist felodipine ER and combined felodipine/simvastatin therapy on retarding the progression of atherosclerosis, estimated by serial changes in coronary calcium evaluated by noninvasive electron beam computed tomography. Subjects include 180 men and women aged 40 to 69 and 50 to 69 years, respectively, with moderate type IIa dyslipidemia, with either cardiovascular disease or risk factors. All subjects receive simvastatin lipid-lowering therapy, and are randomized either to felodipine or placebo for a treatment period of 2 years. Monitoring of blood chemistry, measures of lipids and apolipoproteins, blood pressure, evaluation of symptoms, and interim clinical event monitoring are done at routine follow-up visits. Baseline and 2-year follow-up electron beam computed tomography, measuring changes in total calcium score, area, and mass, evaluate the effects of intervention on the progression of calcified atherosclerosis. The results from the Felodipine Atherosclerosis Prevention Study will provide valuable information about the effect of felodipine alone and in combination with simvastatin on progression of calcified atherosclerosis evaluated noninvasively.