The clinical picture and the course of idiopathic edema is described after evaluating catamnestic questionnaires on 39 patients. It appears that the syndrome often occurs in other female family members, especially in mothers of propositi and that two thirds of patients have also suffered from symptoms of allergy. In contrast to observations of other groups, diabetes mellitus and slight hypoalbuminemia were found only in a few patients. Secondary hyperaldosteronism was almost exclusively observed in patients who had been taking diuretics during the last few days before the measurements were done. The plasma concentrations of 6 other adrenal steroidal hormones were measured in 33 patients. Only in few of them, mostly patients who had taken diuretics, increased level of 11-deoxycorticosterone, 18-OH-11-deoxycorticosterone and corticosterone were observed. Idiopathic edema does not seem to be a disease entity, but some prediposing factor related to the female reproductive system is likely to exist. Results of systematic psychosomatic studies in our patients will be reported later on.