We investigated the effect of sevoflurane and isoflurane on the level of interstitial dopamine of in vivo awake, free moving rats brain striatum using microdialysis techniques. Rats were implanted with a microdialysis probe to the right striatum of the brain and administered with 1.2 MAC of each volatile anesthetics for 1 hour, and dialysates from the probe were determined every 20 minutes. Both anesthetics reduced the amount of dopamine derived from dialysate, and increased the efflux of dopamine with pretreatment of nomifensine 10mg. kg-1 i.p. The change of metabolites of dopamine during anesthesia was increased. No significant difference was found between sevoflurane and isoflurane. We hypothesized that these anesthetics might have special actions on interactions between metabolism and re-uptake of dopamine in rats striatum during anesthesia.