SummaryBackground: In addition to lowering plasma levels of lowdensity lipoprotein cholesterol (LDL-C), statins also raise high-density lipoprotein cholesterol (HDL-C).Hypothesis: Recent studies have shown that treatment with simvastatin results in larger increases in HDL-C than those seen with atorvastatin. The results of three clinical studies are analyzed, comparing the effects of simvastatin and atorvastatin on HDL-C and apolipoprotein A-I (apo A-I) in the total cohort and in several subgroups of hypercholesterolemic patients. The three studies were all multicenter, randomized clinical trials that included simvastatin (20-80 mg) and atorvastatin (10-80 mg) treatment arms. The subgroup analyses performed were gender; age (< 65 and ≥ 65 years); baseline HDL-C (male: <40 or ≥40 mg/dl; female: < 45 or ≥45 mg/dl), baseline LDL-C (< 160 or ≥ 160 mg/dl), and baseline triglycerides (< 200 or ≥ 200 mg/dl).Results: Both drugs produced similar increases in HDL-C levels at low doses; however, at higher drug doses (40 and 80 mg), HDL-C showed a significantly greater increase with simvastatin than with atorvastatin (p < 0.05 to < 0.001). Therefore, while HDL-C remained consistently elevated across all doses of simvastatin, there appeared to be a pattern of decreasing