BACKGROUND: Blood pressure (BP) has a circadian pattern with a morning surge that is associated with an increased risk of acute coronary and cerebrovascular events. In a prospective, randomized, open-label, blinded-endpoint, parallel-group, multicenter, forced-titration study of telmisartan and ramipril, the efficacy of both drugs on mean ambulatory diastolic BP (DBP) and systolic BP (SBP) during the last 6 h of a 24-h dosing interval was evaluated. METHODS: After screening and a single-blind run-in phase, 812 adults with mild-to-moderate hypertension (defined as a mean seated DBP > or =95 mm Hg and < or =109 mm Hg and a 24-h ABPM mean DBP 7 > or = 85 mm Hg) were randomized to the open-label, 14-week, forced-titration, active-treatment phase as follows: telmisartan 40 mg/80 mg/80 mg (n = 405) or ramipril 2.5 mg/5 mg/10 mg (n = 407), once daily in the morning. The primary efficacy variable was change from baseline in the last 6-h mean DBP and SBP at 8 and 14 weeks as assessed by ambulatory BP monitoring (ABPM). Secondary efficacy variables were changes from baseline in BP control during each of the 24-h periods and in-clinic trough cuff BP. RESULTS: Telmisartan 80 mg was superior to ramipril 5 mg and 10 mg in change from baseline in the last 6-h ABPM mean DBP and SBP at both 8 and 14 weeks (both P < .0001), respectively. At 14 weeks, the adjusted mean change from baseline in DBP for telmisartan 80 mg was -8.8 mm Hg compared with that for ramipril 10 mg of -5.4 mm Hg (P < .0001). For SBP, the adjusted mean change from baseline for telmisartan 80 mg was -12.7 mm Hg compared with that for ramipril 10 mg of -7.9 mm Hg (P < .0001). At 14 weeks, telmisartan 80 mg also yielded superior reductions from baseline in trough cuff BP compared with ramipril 10 mg (DBP: -11.0 mm Hg v -7.8 mm Hg, respectively; SBP: -14.3 mm Hg v -9.1 mm Hg, respectively; both P < .0001). Measures of 24-h BP control favored telmisartan 80 mg versus ramipril 10 mg (P < .0001), as did other secondary ABPM endpoints during the daytime, night-time, and morning periods. Treatment-related adverse events were uncommon; patients treated with ramipril had a higher incidence of cough than those treated with telmisartan (10.1% v 1.5%, respectively). CONCLUSIONS: Telmisartan 80 mg was consistently more effective than ramipril 10 mg in reducing both DBP and SBP during the last 6 h of the dosing interval, a measure of the early morning period when patients are at greatest risk of life-threatening cardiovascular and cerebrovascular events. Telmisartan 80 mg was also more effective than ramipril 10 mg in reducing BP throughout the entire 24-h dosing interval. Both drugs were well tolerated.