INTRAVENOUS INFUSIONS of dilute solutions of oxytocin are widely used in obstetrics and gynecology. While it is generally recognized that oxytocin therapy may sometimes endanger mother and fetus by evoking intense myometrial contractions, it is less well appreciated that oxytocin can, under certain circumstances, cause another serious complication, namely, water intoxication. Within a period of 8 months we observed two puerperal women in whom water intoxication developed severe enough to result in convulsions and coma. Both had been delivered very recently and both had received oxytocin plus relatively large volumes of electrolyte-free aqueous fluid intravenously. These two cases as well as controlled experiments illustrating the antidiuretic property of oxytocin will be described. Report of Cases Case 1. A 15-year-old, unmarried, white primigravida was brought to the hospital in active labor on Dec 31, 1961. She was a small individual who prior to this time had successfully concealed her pregnancy from