This open-label, blinded study was performed to evaluate the efficacy and tolerability of barnidipine at a titrated dose of 10 -15 mg once daily for 8 weeks in the treatment of essential hypertension in 40 Thai patients. 'Office' blood pressure (BP) and 24-h ambulatory BP measurements were recorded. A systolic BP/ diastolic BP (SBP/DBP) reduction of 18.0 ± 13.6/9.1 ± 6.6 mmHg was obtained. The full response rate among patients with systolic and diastolic hypertension was 63% using either SBP or DBP criteria, and 54% using both SBP and DBP criteria. One of the two patients with isolated systolic hypertension had a full response, and the BP in two of the three patients with isolated diastolic hypertension was normalized. The trough-to-peak ratio and smoothness index for SBP/DBP were acceptable (0.76 ± 0.63/0.55 ± 0.26 and 1.2 ± 0.4/1.2 ± 0.3, respectively). In conclusion, once-daily barnidipine monotherapy provides effective 24-h BP control and is generally well tolerated in ambulatory patients.