Enflurane is metabolized to inorganic fluoride. Serum levels of inorganic fluoride exceeding 50 microM/l are considered nephrotoxic for normal kidneys. Renal damage has not been observed after enflurane anesthesia in patients with normal renal function. Further impairment in patients with previously damaged kidneys has been reported. The restitution of function of ischemically damaged kidneys was studied in two groups of dogs. In one of the groups, dogs were submitted to a long duration enflurane anesthesia. The other group served as a control. In the first group the serum level of inorganic fluoride at the end of the anesthesia was 27.9 microM/l. Renal function was studied with endogenous clearances and concentration capacity. The inorganic fluoride level achieved by enflurane anesthesia did not influence the restitution of renal function.