OBJECTIVE Evaluate the clinical efficacy and quality of life of indapamide in patients with mild and moderate arterial systemic hypertension under indapamide. METHODS Open prospective design. METHODS Outpatient clinics of the Instituto Nacional de Cardiologia Preventiva in Lisbon. METHODS Thirty-two patients whose supine diastolic blood pressure was between 95 ans 115 mmHg without known secondary hypertension, unstable diabetes, cardiac, renal or hepatic failure, hypokalemia, coronary artery disease or stroke in the previous year. METHODS After a two week wash-out and four week placebo periods, indapamide has been given in a single daily dose of 2.5 mg at breakfast during 12 weeks. RESULTS The mean systolic/diastolic blood pressures was reduced from 155.7/103.7 to 138.6/86.1 mmHg (p < 0.0001). The mean standing systolic/diastolic blood pressure lowered from 160.2/103.7 to 141.6/85.9 mmHg (p < 0.0001). The questionnaires on quality of life and the analogic visual scale showed a progressive and significant improvement in general well-being. In the patient questionnaire the percentage of improvement was 80% (16/20 items) namely asthenia, headache, attention, dizziness, tinnitus and visual disturbance. In the physician questionnaire all the items improved. Biochemical acceptability was characterized by the stability of sodium, chlorine, glucose, creatinine, urea, cholesterol, triglycerides, uric acid and slight decrease in potassium from 4.38 to 4.14 mmol/l (p < 0.01) ranging in normal values. CONCLUSIONS These results confirm the clinical efficacy of indapamide and its beneficial effects on quality of life in patients with mild and moderate hypertension when administered in monotherapy.