When a capillary or renal disturbance is not apparent in a woman of reproductive age who presents with edema, a disorder referred to as idiopathic edema should be considered. This disorder, which is often intermittent, causes fluid to accumulate when the patient is upright. Because of this postural relationship, research into pathogenesis has focused on homeostatic adjustments to changes in posture. A number of mechanisms have been proposed, the most tenable of which seem to be increased capillary permeability, increased mineralocorticoid activity, and a faulty "escape mechanism." The diagnosis of idiopathic edema is established by documenting an excessive intradiem weight gain (greater than 1 kg) and performing a water-loading test. Because the pathogenesis remains obscure, no specific or uniformly successful therapy yet exists. Besides recumbency, restriction of calories, sodium, and fluids may be tried. If these measures do not bring adequate relief, diuretics or sympathomimetics may be prescribed.