The Chiba Lipid Intervention Program (CLIP) Study was designed to clarify the prognosis of Japanese hypercholesterolemic patients taking pravastatin for 5 years. Hypercholesterolemic patients (n = 2,529) with a total cholesterol level > or = 220 mg/dl and without histories of ischemic coronary heart disease and/or cerebral infarction were administered pravastatin (10-20 mg/day). Among them, 2,131 took pravastatin fully (Pravastatin-continued group), and 398 discontinued the treatment (Discontinued group). The baseline total cholesterol level was 264.3 +/- 34.7 mg/dl (mean +/- standard deviation). The mean reduction rates of total cholesterol and low-density lipoprotein (LDL) cholesterol were 18.0% and 27.2%, respectively. Mild and moderate adverse events occurred in 86 cases (3.6%). Serious adverse events were not observed. Death rates of the pravastatin-continued group and of the discontinued group were 2.6 and 16.0/1,000 persons/year, respectively. Cardiac events (fatal and nonfatal myocardial infarction, cardiac death, angina pectoris) in all, occurred in 35 patients (incidence rate = 2.77/1,000 persons/year). In the pravastatin continued group, 9 causes of fatal and nonfatal myocardial infarction occurred (0.84/1,000 persons/year), whereas in the discontinued group, 4 cases occurred (2.06/1,000 persons/ year). The risk ratio for cardiac events was correlated with the number of risks. In the low-risk group (< or = 1 risk), decreased rates of LDL-cholesterol were less in the cardiac event group than the non-cardiac event group (LDL-cholesterol; 16% vs 25%, p = 0.04). These results suggested the following; 1) Pravastatin maintained a cholesterol lowering effect long-term without serious complications. 2) Pravastatin administration might reduce the mortality rate and myocardial infarction. 3) The combination of multiple risks is a strong factor for a cardiac event in addition to hypercholesterolemia.