Candesartan Antihypertensive Survival Evaluation in Japan (CASE-J) trial was conducted to compare the effects of the angiotensin II receptor blocker (ARB) candesartan and the calcium channel blocker (CCB) amlodipine on the incidence of cardiovascular (CV) events in Japanese high-risk hypertensive patients. After 3.2years follow-up, CV events rate was 17.6-17.7 per 1000 person-years in each group, which was much lower than we expected. Since it has not been known whether the same efficacy of two drugs is sustained beyond the current trial, a longer follow-up period will be needed. The Steering Committee of CASE-J trial decided to extend the trial for 3years as an observational study (CASE-J Ex). In CASE-J Ex, the primary end point is a composite of CV events and the secondary endpoints are all-cause death and new-onset diabetes. After Committee's decision, 245 doctors agreed to participate in CASE-J Ex and 2236 patients (1141 with candesartan-based regimens and 1095 with amlodipine-based regimens) were re-enrolled. The baseline characteristics of CASE-J Ex participants were similar to CASE-J participants and still balanced well between candesartan and amlodipine. Recently, the interest of antihypertensive treatment has focused to differentiation of the effects of antihypertensive agents on the incidence of CV events as well as blood pressure lowering effect. CASE-J Ex will clarify the long-term effects of ARB and CCB on CV mortality and morbidity. Additionally, because the number of diabetic patients is increased, the evidences from CASE-J Ex will be valuable.