Hypematremia is usually associated with water depletion. Seven very ill patients developed hypernatremia in association with marked edema during therapy in the hospital. All patients had hypoalbuminemia and azotemia. At the time of hypernatremia, urine output averaged 1880 mL/24 h and urine sodium concentration averaged 59 mmol/L, suggesting that low levels of antidiuretic hormone and/or a diminished effect of this hormone on the nephron may contribute to the pathophysiological mechanism of the hypernatremia. Recognition of this salt- and water-overloaded state should guide therapy.