Observational studies have shown that 24-h and morning ambulatory blood pressure (BP) control is low. This large-scale, practice-based study evaluated the effects of telmisartan 40 or 80 mg alone or in combination with hydrochlorothiazide (HCTZ) 12.5 mg on these BP parameters over 8 weeks; treatment was adjusted if clinic BP remained ≥140/90 mm Hg. A total of 863 patients were evaluated (baseline mean clinic BP, morning and 24-h ambulatory BP: 155±15/93±10 mm Hg, 137±15/83±11 mm Hg, 133±14/79±10 mm Hg, respectively; 68% were previously treated at baseline). Telmisartan with/without HCTZ significantly reduced the mean morning ambulatory BP (-8.2/-4.9 mm Hg), daytime ambulatory BP (-8.0/-4.7 mm Hg), 24-h ambulatory BP (-7.9/-4.7 mm Hg) and clinic BP (-22.3/-13.2 mm Hg) (all P<0.001) in previously untreated and in treated patients who switched to telmisartan and telmisartan/HCTZ. After treatment with telmisartan with/without HCTZ, the morning ambulatory BP control increased from 36.5 to 64.4%; daytime ambulatory BP control increased from 40.8 to 67.6%; 53.0% of patients achieved 24-h ambulatory BP <125/80 mm Hg and 62% achieved <130/80 mm Hg targets. Only 0.8% (7/863) reported an adverse event. In summary, telmisartan and telmisartan/HCTZ increased smooth 24-h BP control in daily management of hypertension.