Serum inorganic fluoride concentrations and their urinary excretion were examined during and after sevoflurane, isoflurane, or enflurane anesthesia in man. Duration of anesthesia was 3 hours in sevoflurane and enflurane groups (S3 group: n = 10, E3 group: n = 5), and 3 or 5 hours in isoflurane groups (I3 group: n = 5, I5 group: n = 5). Serum inorganic fluoride concentration of the S3 and E3 groups increased immediately following induction, and reached the maximum concentration of 21.8 +/- 9.3 (M +/- SD) mumol.l-1 (S3), 13.6 +/- 6.2 mumol.l-1 (E3) at 1 hour after anesthesia. Serum inorganic fluoride decreased after the peak concentrations, and returned to the pre-anesthesia level at 96 hours (S3) and 144 hours (E3) after anesthesia. On the other hand, serum inorganic fluoride of the I3 and I5 groups scarcely changed from the pre-anesthesia level, and maximum concentrations of these two groups were one tenth of the S3 group. Urinary excretion of inorganic fluoride of the S3 and E3 group began to increase from 2 hours after anesthesia, and showed plateau of 60-90 mmol.h-1 from 12 hours to 24 hours after anesthesia. The change of serum inorganic fluoride sharply contrasted with urinary excretion. Our results suggest that fluoride excretion is largely carried out by the kidney. Therefore sevoflurane or enflurane anesthesia should be avoided in patients with renal dysfunction.