The efficacy and tolerability of barnidipine hydrochloride, a once-daily calcium channel blocker, was investigated in 31 Korean patients (19 women and 12 men; mean age, 53 +/- 8 years; mean body weight, 65.8 +/- 9.1 kg) with essential hypertension (mean systolic blood pressure [SEP] and diastolic blood pressure [DBP] in the sitting position, 154.5 +/- 15.9 mm Hg and 101.0 +/- 8.2 mm Hg, respectively). This study used an increasing-dose method with daily doses of 5 to 15 mg in an open-label, uncontrolled manner for 8 weeks. Mean reductions in SEP and DBP after 8 weeks of treatment with barnidipine mere 28.5 mm Hg (mean reduction, 18.4%) and 16.5 mm Hg (mean reduction, 16.3%) in the sitting position, respectively, and the mean dose was 9.7 mg/d, Heart rate in the sitting position was not changed by the administration of barnidipine (mean +/- SD, 70.0 +/- 6.6 beats/min and 71.9 +/- 6.8 beats/min before and after treatment, respectively). Barnidipine was well tolerated, with only mild adverse events such as headache (appearance rare, 6.5%), facial flushing (6.5%), dizziness, nausea, and vomiting (each, 3.2%). These results suggest that barnidipine is a once-daily calcium channel blocker that shows sufficient hypotensive effect and good tolerability in Korean patients with essential hypertension.