The role of central monoamines and the distribution of ethanol to the brain in the genetically determined influences on voluntary ethanol consumption were examined by studying the extracellular levels of ethanol and monoamines in the nucleus accumbens of the alcohol preferring AA (Alko Alcohol) and alcohol avoiding ANA (Alko Non-Alcohol) rats with in vivo microdialysis. The results show that there is a steep rise in brain ethanol concentration within minutes after the injection of ethanol (1 g/kg ip), but there does not seem to be a difference in the distribution of ethanol into the brain of the two lines of rats. There was, however, some indication that ANA rats may absorb ethanol after intragastric administration faster than AA rats. Ethanol (0.5, 1, or 2 g/kg ip) significantly increased the extracellular levels of dopamine, DOPAC, and HVA, but not that of 5-HIAA, suggesting stimulation of dopamine release by ethanol. No difference in the extent or time course of stimulation of dopamine release between the AA and ANA rats was found.