BACKGROUND Cross-sectional studies on human hypertension have suggested an association between sodium intake and left ventricular hypertrophy (LVH). RESULTS The effects on LVH of a nonpharmacological treatment program based mainly on sodium restriction were examined by serial echocardiography in a 12-month controlled, randomized study that included 76 previously untreated subjects with uncomplicated mild-to-moderate hypertension. The mean daily sodium excretion of 38 subjects randomized into the treatment group decreased from 195 +/- 95 to 94 +/- 73 mmol (P < .001) at 6 months and to 109 +/- 74 mmol (P < .001) at 12 months. This was accompanied by a weight decrease from 81.4 +/- 18.0 to 79.2 +/- 17.4 kg (P < .001) at 6 months and to 80.6 +/- 17.5 kg (NS) at 12 months. The net blood pressure decrease (difference in change from baseline between the treatment and control groups) was 8.9 mm Hg (P < .001) in systolic blood pressure and 6.5 mm Hg (P < .001) in diastolic blood pressure during the first 6 months and 6.7 mm Hg (P < .01) in systolic blood pressure and 3.8 mm Hg (P < .01) in diastolic blood pressure during the last 6 months. After 12 months of sodium restriction, left ventricular mass (LVM) had decreased by 5.4% (from 238 +/- 63 to 225 +/- 51 g, P < .01), and LVM index (LVMI) had decreased by 4.7% (from 123 +/- 26 to 117 +/- 22 g/m2, P < .05), whereas no changes occurred in these parameters in the control group. In treated subjects with baseline LVMI of more than the median value of 133 g/m2 in men and 107 g/m2 in women, LVM decreased by 8.6% (from 272 +/- 62 to 249 +/- 51 g, P < .01), and LVMI decreased by 7.1% (from 140 +/- 23 to 130 +/- 22 g/m2, P < .01). LVM and LVMI remained unchanged in treated subjects with LVMI values equal to or less than the median. CONCLUSIONS Our data suggest that long-term nonpharmacological treatment with moderate sodium restriction decreases LVH.