The effect of exogenous ascorbic acid (AA) on acute ethanol-induced decrease in extracellular nitrites contents in striatum of freely moving mice was investigated by using microdialysis coupled to high performance liquid chromatography with electrochemical detection. The results showed that exogenous AA had no effect on basal extracellular levels of nitrites, but significantly increased striatal extracellular contents of AA in a dose-depended manner. Co-administration of AA with ethanol significantly antagonized the ethanol-induced decrease in extracellular nitrites contents, but did not affect ethanol-induced release of AA. These data provided the first evidence of an antagonistic action of AA on ethanol-induced decrease in extracellular nitrites contents in striatum of freely moving mice.