The hemodynamic alt,eretions occurring during anesthesia [1-J] and in surgical diseases [6-81 have been investigated. In recent studies concerned with shock [3,10] some patients were studied postoperatively. Despite this, few reports describe the circulatory alterations which occur after uncomplicated abdominal surgery[ll,l2]. One of the earliest investigations was performed thirty years ago [II] when technics of anesthesia and surgery were significantly different than they are today. Clowes, Del Guercio, and Barwinsky [I,??] studied eight patients before, during, and after major abdominal surgery. Blood loss, estimated from t,he sponges and suction bottle, was totally replaced. Intravenous fluid was restricted to less than 1,000 cc. per square meter of body surface per day. Since operative blood losses less than 500 cc. are not usually replaced, nor intravenous fluids so stringently restricted, the conditions of their study do not reflect those ordinarily encountered in operative and postoperative care. Cyclopropane and ether were the anesthetic agents used in that study, and their effects on the cardiovascular system may have been considerably different than those resulting from halothane anesthesia, which is more commonly used at this time. Shock or other postoperative complications are usually studied in patients who have not ha.d such controlled replacement of blood and fluid in the operative or early postoperative period. In our opinion, therefore, further studies of the effects of abdominal surgery on circulatory