The pattern of postoperative excretion of salt and water has been described by many investigators, and reviewed by Moyer1 and Moore.2 Previous studies have led to the concept of renal intolerance to salt and water in the postoperative period. In many centers, practical application of this concept has resulted in no salt solutions being given to surgical patients during or, for a limited time, after elective operation. This study is designed for observation of the effects of salt solutions given during operation on the postoperative excretion of salt. In this laboratory, using isotopic methods, a significant fall in effective extracellular fluid, greater than that lost as plasma (blood loss), has been observed to occur during the operative period.3 In this study the amount of extracellular fluid loss was correlated with the degree of operative trauma. Administration of salt solutions during operation would represent replacement of the acquired