Enflurane is metabolized in the liver by the hepatic microsomal enzyme system, cytochrome P-450 (P450IIE1) and induces enzyme system during enflurane exposure. Enhanced biotransformation might occur after enflrane itself and pathologic conditions, such as fasting, diabetes, chemical diabetes. Increased inorganic fluoride, one of the enflurane metabolites could impair renal function. The possibility of increased enflurane defluorination in the diabetic patient, group 1 (control, n= 6), group 2 (blood sugar level below 200mg%, n=6) and group 3 (blood sugar level above 200 mg%, n=5), was investigated by measuring the serum and urine F in the preoperative period and 1 MAC-hr, 2 MAC-hr, immediate postoperative and 24th postoprative hour. In the preoperative, iaunediate postoperative and 24th postoperative hour, the changes of renal function were measured by the BUN and creatinine. The results were as follows: 1) In the diabetic groups, serum fluoride ion increased significantly after enflumane anesthesia at a11 time intervals. Between control and group 3, there were significant difference of aerum inorganic fiuoride after enflurane anesthesia. 2) Urine fluoride levels increased significantly after enflurane anesthesia in all groups 3) There were no changes in renal function after enflurane anestheaia. Our study indicated that enflurane dose not harm diabetic patients.