This double-blind study to evaluate long-term efficacy and safety of atorvastatin was performed in 31 community- and university-based research centers in the USA to directly compare a new 3-hydroxy-3-methyl-glutoryl-coenlyme A reductase inhibitor (reductase inhibitor) to an accepted drug of this class in patients with moderate hypercholesterolemia. Participants remained on a cholesterol-lowering diet throughout the study. One thousand forty-nine patients were randomized to receive atorvastatin 10 mg, lovastatin 20 mg, or placebo. At 16 weeks the placebo group was randomized to-either atorvastatin or lovastatin treatment. At 22 weeks, patients who had not met; low-density lipoprotein (LDL) cholesterol target levels doubled the dose of reductase inhibitor. Efficacy evaluation was mean percent change from baseline in LDL cholesterol, triglycerides, total cholesterol, high-density-lipoprotein cholesterol, and apolipoprotein B (apoB). Safety profiles as determined by change from baseline in laboratory evaluations, ophthalmologic parameters, and reporting of adverse events were similar for the 2 reductase inhibitors. After 52 weeks, the atorvastatin group maintained a significantly greater reduction in LDL cholesterol (-37% vs -29%), triglyceride (-16% vs -8%), total cholesterol (-27% vs -21%), and apoB (-30% vs -22%) (p < 0.05). More patients receiving atorvastatin achieved LDL cholesterol target levels than did lovastatin patients (78% vs 63%, respectively), particularly those with coronary heart disease (37% vs 11%, respectively). Atorvastatin is highly effective and well tolerated in patients with primary hypercholesterolemia with no increased risk of adverse events. (C) 1997 by Excerpta Medica, Inc.