This multicentre, open-label extension study to four controlled trials involved 888 patients with mild-to-moderate primary hypertension. Patients received telmisartan 40-80 mg once daily with add-on hydrochlorothiazide (HCTZ; 12.5-25 mg) if necessary and/or other antihypertensives to achieve diastolic blood pressure (DBP) control (<90 mmHg). Treatment continued for up to 4 years. At treatment end, 578 (65.1%) patients were on telmisartan monotherapy, 106 (11.9%) were on telmisartan + HCTZ 12.5 mg, 101 (11.4%) were on telmisartan + HCTZ 25 mg, and 103 (11.6%) were on telmisartan + another antihypertensive + HCTZ. Overall, 84.4% (746/884) patients achieved DBP control. The highest proportion of responders was in the telmisartan monotherapy (40 or 80 mg) treatment category (89.0% 1,511/574 patients]). The mean change in systolic blood pressure (SBP)/DBP from the previous trial baseline to last available trough was -21.2/-17.3 mmHg with telmisartan alone, -24.6/-16.7 mmHg with telmisartan + HCTZ, and - 18.7/-14.9 mmHg with telmisartan + another antihypertensive +/- HCTZ. Most adverse events were of mild-to-moderate intensity and unrelated to treatment. The proportions of patients discontinuing the study due to adverse events, by treatment at onset, were 7.3% (65/888) with telmisartan monotherapy, 6.6% (20/304) with telmisartan + HCTZ and 2.9% (3/103) with telmisartan + another antihypertensive +/- HCTZ. There were 15 deaths during the study, but none was considered drug related. Thus, telmisartan alone or in combination with other antihypertensives achieved and maintained clinically relevant reductions in DBP and SBP. This long-term analysis supports the favourable efficacy and safety profile of telmisartan both as monotherapy and in combination with other antihypertensive drugs.