Hyperlipidemia is primarily implicated in the progression of coronary heart disease (CHD) and its treatment is essential for patients with a history of CHD. Statins such as simvastatin, the lipid-lowering agents, are well-known for their ability to normalize patient's serum lipid levels. The Japan Lipid Intervention Trial study of simvastatin is the first nationwide investigation of the relationship between serum lipid levels and the development of CHD in Japanese patients with hypercholesterolemia. Of 5,127 patients, exclusively with a history of documented CHD at enrollment, 4,673 were treated with open-labeled simvastatin at an initial dose of 5-10 mg/day and were monitored for 6 years. The risk of coronary events tended to be higher in patients with a serum total cholesterol (TC) ≥240 mg/dl compared with total cholesterol <240 mg/dl. The concentration of low-density lipoprotein cholesterol (LDL-C) positively correlated and that of high-density lipoprotein cholesterol (HDL-C) inversely correlated with the risk of CHD. Each 10 mg/dl decrease in LDL-C and each 10 mg/dl increase in HDL-C concentration reduced the risk of CHD by 8.0% (95% confidence interval 3.8-12.0) and 28.3% (95% CI 13.9-40.3), respectively. A reasonable therapeutic strategy to reduce CHD progression in patients with prior CHD under low-dose statin treatment might be regulating the serum LDL-C concentration to at least <120 mg/dl and HDL-C >40 mg/dl, respectively. (Circ J 2002; 66: 1096 - 1100)