The effects of indapamide and captopril on office and ambulatory blood pressure control and on general well-being were investigated in 30 active, randomly selected patients from 25 to 68 years old, with mild to moderate essential hypertension (diastolic blood pressure, 92 to 114 mm Hg). Twenty-four-hour ambulatory blood pressure monitoring using an ICR model 5200 portable recorder and evaluation of general well-being were performed prior to and at the end of three months of therapy with indapamide 2.5 mg given once daily, or captopril 12.5 to 50 mg given twice daily. Indapamide and captopril were equally effective in controlling blood pressures in clinic and during 24-hour activities. Although general well-being and subjective symptomatology improved with both treatments, the only significant difference between the two drugs was improvement in the sleep dysfunction scale with indapamide (p less than 0.02). The results shown in this study suggest that both indapamide (2.5 mg) once daily and captopril (12.5 to 50 mg) twice daily are suitable drugs for initial therapy of active patients with mild to moderate hypertension. A fixed once-daily dosage of an antihypertensive agent may, however, increase patient compliance and convenience.