To the Editor: In discussing the cause of the hyponatremia in 37 patients with cardiac failure, Szatalowicz et al. referred only briefly to fluid intake and the possibility that it may have contributed to the observed hypo-osmolality. We believe that this discussion is insufficient in view of four factors: the well-known clinical problem of dilutional hyponatremia due to excessive water intake; the findings of J. H. Holmes (also from the University of Colorado School of Medicine) of excessive thirst and fluid intake in patients with congestive cardiac failure1, 2; the excessive fluid intake in a reliable canine model of low-output cardiac failure, with resolution of edema and improvement of clinical condition during fluid restriction3; and the intake of as much as 3 liters per day in the patients of Szatalowicz et al. despite plasma hypo-osmolality and volume expansion, which should have tended to reduce fluid intake,4 especially if they were acute in onset. It is a pity, therefore, that fluid intakes were not reported in greater detail, since water intake and presumably inappropriate thirst must have contributed to the hyponatremia and extracellular fluid-volume expansion.