It is controversial regarding to the roles of acetaldehyde and ethanol in the central nervous system. In the present study, the effects of acetaldehyde and ethanol on extracellular levels of glutamate, taurine and GABA in the anterior cingulate cortex (ACC) of freely moving rats were investigated by using the microdialysis technique coupled to high performance liquid chromatography (HPLC) with fluorescent detection. The result showed that glutamate levels were significantly decreased after acute administration of acetaldehyde (AcH, 20 and 100mg/kg, i.p.), while taurine levels were significantly increased after the higher dose of acetaldehyde (100mg/kg, i.p.). GABA levels had no changes at any doses of acetaldehyde tested. Interestingly, similar changes of these amino acids were induced by ethanol (EtOH, 3g/kg, i.p.) when sodium azide (NaN3, 10mg/kg, i.p.), a catalase inhibitor that can reduce brain ethanol metabolism, was used simultaneously. These findings suggest that acetaldehyde and ethanol have the similar effects on the extracellular output of glutamate, taurine and GABA in the ACC.