We have studied the efficiency of urea in the treatment of hyponatremia and hydrosaline retention in a 76-year-old man with chronic ischemic congestive heart failure. Since increase of furosemide worsened the hyponatremia (120 mmol/l), 30 g/day of urea was added and induced the following changes: progressive weight loss (6.5 kg in one week), increased diuresis (from 0.750 to 1.950 l/day), increased salt excretion (from 40 to 165 mmol sodium/day) and correction of the hyponatremia (120 to 136 mmol/l). Blood urea and creatinine serum concentrations rose moderately without significant change in creatinine clearance (32 to 38 ml/min). No adverse effects related to urea administration were observed. Urea intake seems to be useful in the management of hyponatremia in our patient with cardiac failure.