The objective of the study was to assess the efficacy, safety and tolerability of a fixed dose combination of telmisartan 40 mg and hydrochlorothiazide 12.5 mg in adult Indian patients with mild to moderate hypertension. A prospective, multicentric, open-label, non-comparative, phase IV study was conducted. A total of 353 patients of either sex, between 18- 65 years of age with supine blood pressure (BP) levels of systolic BP (SBP) of 140-200 mmHg and diastolic BP (DBP) of 95-114 mmHg were included. After a placebo run-in period of 2 weeks, each patient received a fixed dose combination of telmisartan/hydrochlorothiazide (40mg/12.5mg) once daily, for 8 weeks. Supine BP was assessed at the end of every 2 weeks. Tolerability and safety were assessed by physical examination, laboratory parameters and evaluation of adverse events. A total of 339 patients completed the study with 14 drop-out cases because of loss to follow-up. There was a significant fall (p<0.05) in both the SBP and DBP starting from the second week as compared to the baseline. Mean SBP had a significant reduction of 23.55 mmHg (15.0%) and 27.79 mmHg (18%) at the end of 6th and 8th week respectively, compared to baseline values. Mean DBP had also had a significant reduction of 12.51 mmHg (12.6%) and 15.17 mmHg (15.3%) at the end of 6th and 8th week respectively, compared to baseline values. This combination was well tolerated with only 3.9% of the total cases reporting mild adverse events like fatigue, dizziness, nausea, diarrhoea etc. The laboratory values were within normal limits. Fixed dose combination of telmisartan/hydrochlorothiazide (40 mg/12.5 mg) once daily has a significant therapeutic effect and a good tolerability profile in adult Indian patients with mild to moderate hypertension.