To investigate the changes in renal function during the halothane, enflurane and thalamonal anesthesia and elective surgery, the authors measured urine flow rate, creatinine clearance(Ccr, GFR), excreted amounts of sodium, potassium and chloride ions, fractional excretion of sodium (FeNa), free water clearnace (C H2O) at preanesthesia (control), 20 minute after the induction of anesthesia, during operation (3 times), 1 hour after surgery, respectively, and obtained the results as follows: 1) Changes in renal function was not significant after the induction of anesthesia compared to preanesthesia in halothane, enflurane and thalamonal anesthesia. 2) Renal function decreased signifi-cantly during the operation under anesthesia with halothane or enfiurane. 3) There was a tendency of renal function to be decreased compared to preanesthesia in the 1st postoperative day in patients anesthetized with halothane or enflurane, but tendency of it to be increased in thalamonal anesthesia. Therefore, it is suggested that thalamonal anesthesia is a good choice in patients with renal dysfunc-tion.