In this open-label, non-comparative study, the anti-hypertensive efficacy and effect on left ventricular hypertrophy (LVH) of 24 weeks' treatment with once-daily telmisartan 40-80 mg was evaluated in 24 patients with mild-to-moderate hypertension and LVH. Patients were titrated to the higher dose of study drug at week 4 if they did not achieve blood pressure normalization (i.e. systolic blood pressure [SBP]/diastolic blood pressure [DBP] remained > or = 140/90 mmHg). The anti-hypertensive action of telmisartan was assessed using clinic cuff measurements and 24-h ambulatory blood pressure monitoring, and left ventricular mass index (LVMI) was determined by two-dimensional echocardiography at baseline and after 24 weeks of therapy. Telmisartan significantly reduced mean 24-h, daytime and night-time SBP and DBP compared with baseline after 12 and 24 weeks of therapy. Target blood pressure levels, defined as SBP/DBP < 140/90 mm Hg, were achieved in 16 (69.6%) patients at the end of the treatment period. After 24 weeks of telmisartan treatment, LVMI decreased from 151.6 +/- 5.4 to 135.1 +/- 5.9 g/m2. In conclusion, anti-hypertensive treatment with telmisartan for 24 weeks produced significant reductions in blood pressure and regression of LVH, as assessed by LVMI, in patients with hypertension and LVH.