Objective: To assess the efficacy and acceptability of indapamide sustained-release (SR) monotherapy in elderly high-risk patients with moderate to severe hypertension. Methods: 1277 hypertensive patients older than 55 years with moderate to severe hypertension, including 91% with systolic blood pressure (SBP) >160 mmHg and at least one cardiovascular risk factor (age >65 years, male, diabetes mellitus, coronary heart disease [CHD], cerebrovascular disease, dyslipidaemia, obesity, smoking) were enrolled in this observational study. They received indapamide SR 1.5 mg, one tablet daily, for 3 months. Blood pressure (BP) was assessed monthly by sphygmomanometer. Statistical analyses were performed using the χ2 test, analysis of variance, and the Newman-Keuls test. Results: After 3 months of treatment with indapamide SR, SBP had decreased by 34 ± 3 mmHg and diastolic BP (DBP) by 12 ± 6 mmHg (both p < 0.001). Ninety-two percent of patients responded to therapy (SBP/DBP reduction >20/10 mmHg) and 52% were normalized (SBP <140 mmHg and DBP <90 mmHg). BP targets were reached in 48% of patients older than 65 years, 31% of diabetic patients, and 33% of patients with CHD. There were no changes in serum creatinine, glucose or lipid parameters, and 3% of patients had hypokalaemia (<3.5 mmol/L). The patients self-assessment scores regarding general state of health improved and 34% of patients reported 'excellent' health after treatment. Conclusions: In the high-risk patients of the ARGUS study, monotherapy with indapamide SR showed antihypertensive efficacy with good acceptability and no changes in metabolic parameters over a 3-month period. Indapamide SR monotherapy normalized BP in half of the patients treated and proved an appropriate first-line treatment in hypertensive patients older than 55 years with added cardiovascular risk factors. © 2008 Adis Data Information BV. All rights reserved.