The constellation of risk factors known as the metabolic syndrome increases the risk of coronary artery disease at any low-density lipoprotein (LDL) cholesterol level. We performed an exploratory analysis of data from 5 trials to study the effects of rosuvastatin 10 mg on lipid levels and ratios in hypercholesterolemic patients (LDL cholesterol > or =160 mg/dL and <250 mg/dL) who met a modified National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) definition of the metabolic syndrome. Of 580 patients completing 12 weeks of treatment with rosuvastatin 10 mg, 194 (33%) met the definition of the metabolic syndrome by exhibiting > or =3 of the following: body mass index >30; triglycerides > or =150 mg/dL; high-density lipoprotein (HDL) cholesterol <40 mg/dL in men and <50 mg/dL in women; blood pressure > or =130/> or =85 mm Hg or receiving current medication for hypertension; and fasting blood glucose > or =110 mg/dL. Patients with the metabolic syndrome had higher triglyceride, non-HDL cholesterol, apolipoprotein B, and lipid ratios, and lower HDL cholesterol and apolipoprotein A-I levels, at baseline compared with patients without the metabolic syndrome. In patients with the metabolic syndrome, rosuvastatin 10 mg improved LDL cholesterol (-47%), non-HDL cholesterol (-43%), non-HDL cholesterol/HDL cholesterol ratio (-47%), apolipoprotein B (-37%), apolipoprotein B/apolipoprotein A-I ratio (-40%), triglycerides (-23%), apolipoprotein A-I (+7%), and HDL cholesterol (+10%)-in a manner similar to that in hypercholesterolemic patients who did not meet these criteria. Among patients who met the metabolic syndrome criteria and who had triglycerides > or =200 mg/dL, 64% met their ATP III non-HDL goals.