BACKGROUND: This study was designed to evaluate the clinical efficacy of pravastatin, HMG-CoA reductase inhibitor, in patients with hypercholesterolemia. Methods and RESULTS: Pravastatin 5 mg was administered twice daily for 12 weeks in twenty five patients(12 male, 13 female) with hypercholesterolemia(>240 mg/dl). Compared with pretreatment levels, pravastatin significantly decreased levels of total cholesterol(281+/-41mg/dl versus 218+/-31mg/dl) by 22% and LDL-cholesterol(199+/-46mg/dl versus 137+/-37mg/dl) by 31% with significantly decreased total-cholesterol/HDL-cholesterol ratio(7.1+/-3.0 versus 5.1+/-1.6) and LDL-cholesterol/HDL-cholesterol ratio(5.1+/-2.5 versus 3.3+/-1.4) (p<0.005, respectively). During pravastatin treatment, the level of Apo B(164+/-38mg/dl versus 123+/-20mg/dl) was decreased significantly by 24% with significantly decreased Apo B/Apo A-1 ratio(1.4+/-0.5 versus 1.0+/-0.3) (p<0.005, respectively). No serious side effects were found. CONCLUSIONS: Results from the present study show that pravastatin is an effective and well-tolerated cholesterol-lowering agent.