The objective of this study was to evaluate the safety and efficacy of indapamide 1.25 mg once daily as monotherapy in elderly patients (65 years and older) with mild to moderate essential hypertension. Two hundred and seventy-nine (279) elderly patients were enrolled in a washout period, during which patients received single-blind placebo for 4 weeks. Patients demonstrating supine diastolic pressures between 95 mm Hg and 114 mm Hg at the end of the 4-week placebo washout period were entered into the 8-week double-blind treatment period. Two hundred and four (204) patients qualified for the study and were randomized to the double-blind treatment; 103 patients received indapamide 1.25 mg and 101 patients received placebo for 8 weeks. Overall, 177 patients (92 indapamide and 85 placebo) completed the study. The primary efficacy criterion was the mean change in supine diastolic blood pressure (DBP) from double-blind baseline to the end of 8 weeks of therapy. By week 8 of the double-blind treatment period, indapamide 1.25 mg produced a statistically significant (P = 0.0037) decrease in supine DBP of 8.2 mm Hg compared to a decrease of 5.3 mm Hg produced in the placebo group. Additionally, indapamide 1.25 mg was statistically (P = 0.0028) more effective than placebo in reducing supine systolic BP (SBP) (-10.1 vs -4.2 mm Hg). The incidence of drug-related adverse events during the double-blind treatment period was similar between the two treatment groups. A low dose of indapamide, 1.25 mg, given once daily for 8 weeks was effective as monotherapy with respect to BP reduction in an elderly population with mild to moderate hypertension. Indapamide 1.25 mg was safe and generally well tolerated in this elderly patient population.