We tested the hypothesis that, compared with placebo, simvastatin would reduce the progression of coronary artery calcium (CAC) and abdominal aortic calcium (AAC) levels in participants asymptomatic for vascular disease. Total CAC and AAC were measured with multidetector cardiac computed tomography. Inclusion criteria were a CAC score of >or=50 Agatston units, high-density lipoprotein (HDL) cholesterol level<or=50 mg/dl, low-density lipoprotein (LDL) cholesterol level between 100 and 160 mg/dl, and >or=2 other risk factors. Diabetes and history of vascular disease were exclusion criteria. Participants were randomized to receive 80 mg simvastatin (n=40) or matching placebo (n=40) for 12 months. Lipids were measured at 3-month intervals, and CAC and AAC measurements were repeated at 6 and 12 months. Total cholesterol, triglycerides, and LDL decreased significantly with simvastatin treatment (p<0.0001 for all comparisons, adjusted for baseline levels), whereas lipids remained unchanged for subjects randomized to receive placebo. Total CAC volume increased from baseline in both treatment groups. For subjects in the active treatment group, CAC volume increased by 9%, whereas in the placebo group, plaque volume increased by 5% (p=0.12 for treatment effect). AAC volume also increased in both treatment groups (p=0.15 for treatment effect). In conclusion, simvastatin treatment does not reduce progression of CAC or AAC compared with placebo.