Spontaneous hyponatremia in cirrhosis with ascites is generally considered to be due to an impaired renal ability to excrete free water, to be a contraindication of diuretics, and to be a bad prognostic sign. These concepts are reviewed in this paper. 55 cirrhotics with ascites were divided into three groups. Group I consisted of 13 patients with hyponatremia and very low free-water clearance CH2O, 0.07 +/- 0.26 ml/min). These patients also had poor renal function: low inulin clearance (CINU, 40.6 +/- 25.9 ml/min) and paraaminohippurate clearance (CPAH, 383 +/- 275 ml/min). Group II consisted of 8 patients who also had hyponatremia. CH2O, CINU, and CPAH in these patients were fairly high: 5.85 +/- 1.53 ml/min, 85.7 +/- 26.2 ml/min, and 651 +/- 294 ml/min. These values are similar to those o7 +/- 4.27 ml/min, 94.7 +/- 33.1 ml/min, and 598 +/- 199 ml/min. Hyponatremia in Group I could be related to the impaired free-water clearance. The mechanism of hyponatremia in Group II patients is not clear. Patients with hyponatremia and low CINU and CPAH had a negative response to diuretics and a poor prognosis. Patients with hyponatremia but with relatively good renal function had a good prognosis, similar to Group III patients. They responded to diuretics with no worsening of their hyponatremia.