This study is designed as an open label study. After a 2-week placebo run-in phase, qualified patients will be administered with telmisartan 80mg for 2 weeks, then forcefully titrated to telmisartan 80 mg and hydrochlorothiazide 12.5 mg fixed dose combination for 6 weeks. 24 hour ABPM will be performed at the end of placebo run-in period (baseline) and after 8 weeks of active treatment.