This multicenter, randomized, double-blind, placebo-controlled clinical study assessed the efficacy and safety of ezetimibe administered with lovastatin in primary hypercholesterolemia. After dietary stabilization, a 2- to 12-week washout period, and a 4-week single-blind placebo lead-in period, 548 patients with low-density lipoprotein (LDL) cholesterol > or =145 mg/dl (3.75 mmol/L) and < or =250 mg/dl (6.47 mmol/L) and triglycerides < or =350 mg/dl (3.99 mmol/L) were randomized to one of the following, administered daily for 12 weeks: ezetimibe 10 mg; lovastatin 10, 20, or 40 mg; ezetimibe 10 mg plus lovastatin 10, 20, or 40 mg; or placebo. The primary efficacy variable was percentage decrease in direct LDL cholesterol from baseline to end point for pooled ezetimibe plus lovastatin versus pooled lovastatin alone. Ezetimibe plus lovastatin significantly improved concentrations of LDL cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides compared with lovastatin alone (p <0.01). The coadministration of ezetimibe provided an incremental 14% LDL cholesterol decrease, a 5% HDL cholesterol increase, and a 10% decrease in triglycerides compared with pooled lovastatin alone. Ezetimibe plus lovastatin provided mean LDL cholesterol decreases of 33% to 45%, median triglyceride decreases of 19% to 27%, and mean HDL cholesterol increases of 8% to 9%, depending on the statin dose. The coadministration of ezetimibe 10 mg plus the starting dose of lovastatin (10 mg) provided comparable efficacy to high-dose lovastatin (40 mg) across the lipid profile (LDL cholesterol, HDL cholesterol, and triglycerides). Ezetimibe plus lovastatin was well tolerated, with a safety profile similar to both lovastatin alone and placebo. The coadministration of ezetimibe and lovastatin may offer a new treatment option in lipid management of patients with hypercholesterolemia.