Rosuvastatin, a new hydrophilic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin), is approved as an adjunct to diet in patients with primary hypercholesterolemia, mixed dyslipidemia, or Fredrickson type IV hypercholesterolemia. Because of its increased affinity for the reductase, rosuvastatin reduces the low-density lipoprotein cholesterol (LDL) level more than atorvastatin, simvastatin, and pravastatin do, without additional adverse effects. In addition, cytochrome P450 isoenzymes do not extensively metabolize rosuvastatin, and inhibitors of these isoenzymes do not substantially affect it. Rosuvastatin could be a first-line option for patients requiring a reduction of 50% or more to reach the LDL goal of the National Cholesterol Education Program Adult Treatment Panel III. Rosuvastatin monotherapy may allow patients to achieve this LDL goal earlier, and it may help them avoid combination therapy or potential adverse effects of high-dose statin therapy. However, because cardiovascular disease morbidity and mortality data are lacking for rosuvastatin (but available for all other marketed statins) and because its postmarketing data are limited, rosuvastatin should be reserved for patients requiring an LDL reduction of 50% or less who cannot reach the recommended goal with other statins because of adverse effects, drug interactions, or cost.