Indapamide, a sulphonamide derivative, was prescribed for 8 weeks at low dose (2.5 mg once a day) to 14 hypertensive patients in order to investigate its effects on systolic and diastolic blood pressure (SBP, DBP), cardiac function and peripheral arterial resistance (PAR). During treatment we observed decreases in both SBP and DBP without any change in HR in the supine and standing positions and on exercise. As a result cardiac work was significantly reduced. Slight changes in pre-ejection period (PEP) and left ventricular ejection time (LVET) along with a more significant decrease in rate of rise of left ventricular pressure (DBP to PEP ratio) were observed during treatment. An increase in RBF and a decrease in PAR were also detected in the peripheral circulation. These findings may indicate that indapamide antagonizes the cardiovascular effects of catecholamines.