The purpose of Holicos-PAT was to investigate the efficacy of serum lipid lowering by pravastatin against coronary heart disease (CHD) and cerebrovascular disease (CVD) in the Japanese population. Hypercholesterolemic men and women (n = 2,232), aged 40-70 years, were followed up for 5 years, while they were receiving pravastatin (group P, n = 1,422) or only diet therapy (group C, n = 810). The primary endpoint was CHD (a composite of onset or worsening of angina pectoris, performing CABG or PTCA, non-fatal myocardial infarction, death from CHD including heart death or sudden death). The secondary endpoints were comprised of CVD, total mortality, variation of serum lipid and apoprotein levels, and a relationship between the LDL-C level and occurrence of CHD. For several reasons (proving to meet the exclusion criteria after registration, etc.), 1,290 cases of group P and 749 cases of group C were used as subjects for the primary analysis. The mean follow-up period was 4.5 years in group P and 4.2 years in group C for events of CHD. The mean LDL-C level (SD) in group P was 176 (29) mg/dl and decreased to 134 (29) mg/dl one year later. This effect continued during the follow-up period. CHD events occurred in 9.2/1000 patient-years for men and 2.4/1000 patient-years for women without a history of CHD. CHD events occurred in 55.3/1000 patient-years for men and 23.6/1000 patient-years for women with a history of CHD, which was 6 times higher in men and 10 times higher in women than in those without a history of CHD, respectively. The adjusted relative risk ratio of group P to group C for CHD events was 0.74 (95%Cl: 0.47-1.19). In the patients with a history of CHD, the ratio was 0.55 (95%Cl: 0.30-1.00). The effect was apparent in the patients with a history of CHD. The incidence of myocardial infarction in Japanese patients with hypercholesterolemia living in the Hokuriku district was apparently lower, than the worldwide incidence, indicative that pravastatin may have a tendency to inhibit the occurrence of events of arteriosclerotic disease.