Twelve patients with surgical diseases were operated on without any aid of the auxiliary treatment, either preliminary or postoperative, and they were studied for the serum electrolyte concentration as well as for the metabolic balance of electrolytes, including sodium, potassium, calcium, magnsium, chloloride, bicarbonate, phosphate and water, during the whole period of three weeks covering the preoperative ( one week ) and the postoperative (two weeks ) stages.