Conventional lipid-lowering agents displayed only limited efficacy in lowering total and LDL cholesterol and a high incidence of side effects. Pravastatin is a new potent cholesterol-lowering agent, which selectively inhibits hepatic HMG-CoA-reductase. In a double-blind, placebo-controlled Swiss multicenter study with determination of lipids and lipoprotein in a central laboratory, the efficacy and safety of 6 months' therapy with pravastatin was evaluated in 50 patients with mild hypercholesterolemia and additional coronary risk factors. Compared to baseline and after 26 weeks' therapy, pravastatin significantly reduced total cholesterol (pravastatin vs placebo, -17% vs +7%, p < 0.0001) and LDL cholesterol (-26 vs +2%, p < 0.0001). The total/HDL cholesterol ratio ( = "atherogenic index") was comparable in the two groups at baseline (5.9 +/- 1.1 vs 6.3 +/- 0.9), and was distinctly lowered by pravastatin but not placebo (-20 vs 0%, p < 0.0001). In 11 patients in whom the reduction of serum total cholesterol after 13 weeks' treatment with 20 mg pravastatin was still below target (on average -9.1%), doubling of the dose produced a further decrease of 4.3%. Serum HDL cholesterol and serum triglyceride levels did not change significantly during pravastatin treatment as compared to baseline and placebo. Pravastatin was well tolerated during the 26 weeks without relevant subjective side-effects. There were 5 dropouts during the study, 2 patients in the pravastatin group and 3 in the placebo group. These findings document that pravastatin, administered in a single daily dose of 20 to 40 mg, effectively lowers serum cholesterol and total-/HDL-cholesterol improving action and is well tolerated.