The aim of the present study was to evaluate the effects of a normal-sodium (120 mmol sodium) diet compared with a low-sodium diet (80 mmol sodium) on readmissions for CHF (congestive heart failure) during 180 days of follow-up in compensated patients with CHF. A total of 232 compensated CHF patients (88 female and 144 male; New York Heart Association class II-IV; 55-83 years of age, ejection fraction <35% and serum creatinine <2 mg/dl) were randomized into two groups: group 1 contained 118 patients (45 females and 73 males) receiving a normal-sodium diet plus oral furosemide [250-500 mg, b.i.d. (twice a day)]; and group 2 contained 114 patients (43 females and 71 males) receiving a low-sodium diet plus oral furosemide (250-500 mg, b.i.d.). The treatment was given at 30 days after discharge and for 180 days, in association with a fluid intake of 1000 ml per day. Signs of CHF, body weight, blood pressure, heart rate, laboratory parameters, ECG, echocardiogram, levels of BNP (brain natriuretic peptide) and aldosterone levels, and PRA (plasma renin activity) were examined at baseline (30 days after discharge) and after 180 days. The normal-sodium group had a significant reduction (P<0.05) in readmissions. BNP values were lower in the normal-sodium group compared with the low sodium group (685+/-255 compared with 425+/-125 pg/ml respectively; P<0.0001). Significant (P<0.0001) increases in aldosterone and PRA were observed in the low-sodium group during follow-up, whereas the normal-sodium group had a small significant reduction (P=0.039) in aldosterone levels and no significant difference in PRA. After 180 days of follow-up, aldosterone levels and PRA were significantly (P<0.0001) higher in the low-sodium group. The normal-sodium group had a lower incidence of rehospitalization during follow-up and a significant decrease in plasma BNP and aldosterone levels, and PRA. The results of the present study show that a normal-sodium diet improves outcome, and sodium depletion has detrimental renal and neurohormonal effects with worse clinical outcome in compensated CHF patients. Further studies are required to determine if this is due to a high dose of diuretic or the low-sodium diet.