Background: Effects of Cilnidipine versus Atenolol on Left Ventricular Diastolic Function and Hypertrophy in Essential Hypertension (CANDLE) study was designed as a prospective, randomized, double-blind, parallel-group to test whether cilnidipine achieves greater left ventricular (LV) mass reduction and improves LV diastolic function than does atenolol. Methods: Seventy-two patients with uncomplicated essential hypertension and increased LV mass index at screening echocardiography were randomly assigned and forced-titrated to 20 mg/d cilnidipine or 100 mg of atenolol for 36 weeks. Echocardiography, ambulatory blood pressure monitoring, biochemical studies including NT pro-BNP and 24-hours urine microalbumin were measured at baseline and after 36-weeks therapy. Results: Clinical examination and blinded echocardiogram in a per-protocol analysis of 28 cilnidipine-treated and 26 atenolol-treated patients revealed similar reductions in systolic/diastolic pressure (-16.5/8.9 versus -23.9/14.8 mmHg) and LV mass index (-21.4 versus -19.5 g/m²). Interestingly, cilnidipine-treated group showed reduction on left atrial (LA) volume index but atenolol-treated group showed more enlarged LA (-5.1 versus 7.3 %, p=0.035). Conclusions: Both cilnidipine and atenolol similarly and effectively reduced blood pressure and LV mass index. However, only cilnidipine reduced LA volume index, whereas atenolol increased. Cilnidipine may provide more beneficial effect on the management in essential hypertension with diastolic dysfunction.