BACKGROUND Telmisartan provides effective treatment of hypertension in a broad spectrum of patients. AIMS To evaluate factors affecting the efficacy of telmisartan in daily clinical practice. SETTING AND DESIGN Prospective practice-based 12-week uncontrolled cohort study. MATERIALS AND METHODS Consecutive incident/prevalent outpatients with mild to moderate essential hypertension were started on telmisartan 40 mg/day with optional up-titration to 80 mg/day in order to achieve seated systolic (SSBP) and diastolic (SDBP) blood pressure < 140/90 mm Hg. Intent-to-treat (ITT, N=282) and per protocol (PP, N=275) efficacy assessment was based on SSBP/SDBP reduction and delivered doses. RESULTS SSBP/SDBP decreased (165.2+/-13.1 / 98.3+/-6.7 mm Hg to 137.9+/-13.2 / 82.6+/-7.3 mm Hg), whilst telmisartan was up-titrated in 40.5% of patients during the study. Multivariate (practically identical ITT and PP) analysis indicated poorer response in obese vs. non-obese patients: lesser SDBP reduction (by around 2.2-2.3 mm Hg, P < 0.05) with higher odds of dose up-titration (odds ratio, OR around 1.90, P < 0.05); and better response in: a) patients started on telmisartan monotherapy than when added to a preexisting treatment: greater SSBP/SDBP reduction (by around 4.0 and 3.0 mm Hg, respectively, P < 0.05) with comparable odds of up-titration; b) diabetics vs. non-diabetics: greater SDBP reduction (by around 3.6-3.7 mm Hg, P < 0.05) with comparable odds of up-titration; c) men vs. women: slightly greater SDBP reduction (by around 1.2 mm Hg, 0.05 P < 0.1) with lower odds of up-titration (OR around 0.51, P < 0.05). CONCLUSION Previous unsuccessful treatment, obesity, diabetes and gender should be considered in order to optimize the use of telmisartan for mild to moderate essential hypertension in daily clinical practice.