Objective:To compare the effect of lercanidipine and felodipine on day-by-day blood pressure variability (BPV) measured by home blood pressure monitoring (HBPM).Methods:As a substudy of a multi-center, randomized clinical trial: Lercanidipine hydrochloride versus Felodipine sustained-release for mild-to-moderate hypertension, this study lasted 8 weeks, 2 run-in weeks and 6 treatment weeks.Atotal of 281 adult patients (18-75 years) with mild to moderate primary hypertension were randomized to lercanidipine group (administered lercanidipine 10 mg/d) or felodipine group (administered felodipine 5rng/d), and measured HBPM by a validated oscillometric device (HEM7112; Omron Healthcare) 3 limes each morning and 3 times each evening for 42 consecutive days (from one week before randomization to week 6 after treatment), Office BP at each visit and ambulatory BP monitoring (ABPM) at baseline and the endpoint Day-by-day home BPV was defined as the SD of daily BP average (average of 6 readings) of 7 consecutive days.