The effect of systemic ethanol administration on the extracellular levels of glutamate in the hippocampus and nucleus accumbens of conscious rats was assessed using microdialysis. At 0.5 g/kg, ethanol caused a sustained increase in the levels of glutamate in both regions. Following 1.0 g/kg, response was observed in the nucleus accumbens while a trend towards a decrease in glutamate levels occurred in hippocampus. Injection of 2.0 g/kg ethanol decreased these levels in both regions. These findings suggest a relationship between the previously reported biphasic behavioral consequence of ethanol and its effect on glutamatergic neurotransmission.