Left ventricular hypertrophy is a major and independent cardiovascular risk factor in hypertension. The effects of a diuretic, indapamide, on the regression of left ventricular hypertrophy were studied in a group of 9 patients with mild hypertension treated in an open therapeutic trial over a 12 month period. At the end of the trial, the left ventricular mass index decreased significantly from 172 +/- 11 to 147 +/- 11 g/m2 (p less than 0.001). Therefore, in contrast to the other diuretics which have been studied, indapamide seems able to induce regression of the left ventricular hypertrophy complicating hypertension.