Coronary events and stroke are leading causes of death in Japan. However, the effects of hypertension on the risk of coronary events and stroke have not been well established in Japanese hypercholesterolemic patients. This study aimed to determine the relationship between the risk of coronary events or stroke and blood pressure and cholesterol levels during low-dose simvastatin treatment using data from the Japan Lipid Intervention Trial (J-LIT) study (a large scale nationwide cohort study). In the present study, 47,294 hypercholesterolemic patients were treated with open-labeled simvastatin (5 to 10 mg/day) for 6 years by a large number of physicians in a clinical setting. The adjusted incidence rates of coronary events in males and females were 8.9 and 2.3 and those of stroke were 17.6 and 11.3/1000 patients during the 6-year period, respectively. The incidence rate of stroke was higher than that of coronary events in both males and females. An obvious sex difference was observed in terms of the incidence of coronary events. The risk of coronary events, stroke, and total cardiovascular events were increased, with elevations in blood pressure observed in patients treated for hypercholesterolemia. The risk of total cardiovascular events in the groups exhibiting less lipid control increased, with lower blood pressure levels than those of the well-controlled group. For patients with hypercholesterolemia and hypertension, blood pressure should be strictly controlled in order to prevent both coronary events and stroke, and the serum total cholesterol levels should be maintained at low levels as well.