This open-label, multicentre, multinational trial evaluated the efficacy and safety of telmisartan used alone or as add-on therapy in 2121 adults with mild-to-moderate essential hypertension. Patients received telmisartan 40-80 mg once daily for 12 weeks and could participate in the study for up to 96 weeks, or until a marketed supply of telmisartan became available. Mean change from baseline in mean seated trough diastolic blood pressure (DBP) after 12 weeks' treatment, the primary endpoint, was -11.8 mmHg in the intent-to-treat population. The corresponding mean change in mean seated trough systolic blood pressure (SBP) was -20.2 mmHg. Both changes were statistically significant. Mean DBP and SBP reductions were apparent from week 4 and maintained throughout the treatment period. Telmisartan was well tolerated; the most common adverse events were headache (6%) and dizziness (3%), and 10% of adverse events were considered drug-related. In conclusion, telmisartan is an effective and well-tolerated drug when used as monotherapy or add-on treatment in this broad population of patients.