In a double-blind, randomized, placebo-controlled, parallel-group study the ambulatory blood pressure monitoring (ABPM) and relative tolerability of different doses of manidipine hydrochloride (10, 20 and 40 mg) were compared to placebo in patients with mild to moderate essential hypertension. After an initial 2-week run-in period on placebo, 52 patients, 32 males and 20 females, aged 40 to 63 years, were randomized to receive manidipine 10 mg, 20 mg, 40 mg or placebo, all administered once daily for 4 weeks. Patients were checked after the initial placebo phase and every 2 weeks thereafter. At each visit, casual BP and HR were measured. At the end of the placebo period and after 4 weeks of active treatment, non-invasive 24-h ABPM was performed. 24-h, day-time and night-time ambulatory BP as well as the area under the curve (AUC) and casual BP were dose-dependently reduced by manidipine 10, 20 and 40 mg, without changes in the normal BP circadian profile. The trough:peak ratio for both SBP and DBP was higher than 50% for all three manidipine dosage regimens. The percentage of abnormal ambulatory SBP and DBP readings was significantly reduced in all manidipine-treated groups versus placebo. The risk/benefit ratio suggests that the intermediate manidipine dosage (20 mg) could be a suitable dose regimen for the majority of patients with mild to moderate hypertension.