This study was designed to compare the effect of candesartan on cardiac left ventricular mass in Japanese patients with that of amlodipine. A total of 40 type 2 diabetic patients with hypertension and left ventricular hypertrophy (LVH) were randomly assigned to receive candesartan (n=20) or amlodipine (n=20). The two treatments when administered for 6 months significantly reduced systolic and diastolic blood pressures (BPs) to a comparable extent. Notably, candesartan significantly reduced left ventricular mass index (LVMI: from 131.5+/-4.5 to 112.1+/-5.9g/m(2), P=0.0009, M+/-S.E.M.), LV posterior wall thickness (PWTd: from 10.3+/-0.3 to 9.1+/-0.3mm, P=0.0052) and interventricular septal thickness (IVSTd: from 10.7+/-0.4 to 9.3+/-0.4mm, P=0.0019) as determined by echocardiography in diastole, but amlodipine treatment did not. LVMI, PWTd and IVSTd were decreased more significantly by the treatment with candesartan than by that with amlodipine (P=0.020, 0.031 and 0.043). The present study thus revealed that candesartan effectively induced regression of LVH in type 2 diabetic patients with hypertension due to effects beyond reduction in BP.