['Use of 3-hydroxyl-3-methylglutaryl-3 coenzyme A reductase (HMGCR) inhibitors, or statins, reduces cardiovascular disease risk by lowering plasma low-density lipoprotein cholesterol (LDL-C) concentrations. However, LDL-C response is variable and influenced by many factors, including racial ancestry, with attenuated response in blacks compared with whites. We hypothesized that single nucleotide polymorphisms in the gene encoding HMGCR, a rate-limiting enzyme in cholesterol synthesis and the direct enzymatic target of statins, contribute to variation in statin response.', 'Genomic resequencing of HMGCR in 24 blacks and 23 whites identified 79 single nucleotide polymorphisms. Eleven single nucleotide polymorphisms were selected to tag common linkage disequilibrium clusters. These single nucleotide polymorphisms and the common haplotypes inferred from them were tested for association with plasma LDL-C and LDL-C response to simvastatin treatment (40 mg/d for 6 weeks) in 326 blacks and 596 whites. Black carriers of H7 and/or H2 had significantly lower baseline LDL-C (P=0.0006) and significantly attenuated LDL-C response compared with black participants who did not carry either haplotype as measured by absolute response (-1.23+/-0.04 mmol/L, n=209, versus -1.45+/-0.06 mmol/L, n=117; P=0.0008) and percent response (-36.9+/-1.0% versus -40.6+/-1.3%; P=0.02), but no haplotype effect was observed in whites. Percent LDL-C response was lowest in carriers of both H2 and H7, all but one of whom were black (-28.2+/-4.9%, n=12 H2+H7 carriers, versus -41.5+/-0.5%, n=650 H2/H7 noncarriers; P=0.001). LDL-C responses in H7 and/or H2 noncarriers were indistinguishable between blacks and whites.'] Is variation in the 3-hydroxyl-3-methylglutaryl coenzyme a reductase gene associated with racial differences in low-density lipoprotein cholesterol response to simvastatin treatment?