Normotensive women after toxemia of pregnancy reacted to the infusion of reconstituted human plasma with a water diuresis, whereas control subjects exhibited an antidiuretic response. The latter was probably due to the presence of antidiuretic material in the infused plasma, whereas the water diuresis, which has also been found in hypertensive subjects, can be explained as the manifestation of an increased sensitivity of a volume-regulating mechanism in the hypertensive as well as in the “pre-hypertensive” state.