Ten women with "idiopathic" edema had sodium and water retention and a rapid gain in weight when their accustomed intake of diuretics was suddenly stopped. The magnitude of these changes was directly related to the levels of plasma-rening activity before withdrawal of diuretics. Nine patients became edematous. Within 10 days of stopping diuretics, plasma-renin activity and urinary aldosterone excretion decreased to normal or below and within 20 days weight-gain and edema had subsided in seven patients. But the greatest gains in weight, in three patients, were sustained beyond 20 days. Nevertheless, a year later, two of these three patients were free of edema without the use of diuretics. Intermittent edema of unknown cause in most, if not all, otherwise healthy women seems to result from their use of diuretics, abetted in some patients by self-imposed flucuation of sodium and carbohydrate intake, and does not appear to be idiopathic.