The impact of an ARB, with or without hydrochlorothiazide (HCTZ), on glycaemic factors and the risk for developing diabetes in hypertensive patients with the metabolic syndrome have not been fully assessed. This was a 52-week multicentre, prospective, phase-IV, open-label, cohort study of losartan or losartan/HCTZ in hypertensive patients with metabolic syndrome. All subjects were treated initially with losartan 50 mg day(-1). Those not achieving target blood pressure (BP <140/90 mm Hg) were titrated sequentially to losartan 100 mg, losartan 100 mg/HCTZ 12.5 mg, losartan 100 mg/HCTZ 25 mg and finally to losartan 100 mg/HCTZ 25 mg and calcium-channel blocker (CCB), as required. The primary glycaemic outcome measure was change in fasting blood glucose (FBG) and glycosylated haemoglobin A1c (HbA1c) at 52 weeks of treatment. Among the 1897 potentially eligible patients enrolled in the study, 1714 fulfilled the screening criteria. During the 52-week treatment period of the study, FBG and HbA1c did not change significantly. Clinically important and statistically significant changes were observed for both the systolic (SBP) and diastolic BP (DBP) during the study treatment period, with an overall mean decrease of 16.95 mm Hg in SBP (P=0.001) and 9.84 mm Hg in DBP (P=0.001). The majority of the patients (77.3%) achieved a target BP of <140/90 mm Hg. In conclusion, losartan, either alone or in combination with HCTZ, is effective in managing hypertension without inducing any change in glycaemic parameters or increasing the risk for developing diabetes in hypertensive patients with the metabolic syndrome.