Concentrations of norepinephrine (NE), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were determined in eleven brain regions of rats following acute and repeated ethanol administration: (a) an intraperitoneal (i.p.) injection of 1, 2, 3 or 4g ethanol/kg body weight and (b) i.p. injection of 1 or 2g ethanol/kg body weight for seven consecutive days. After acute administration, the concentrations of monoamines and their metabolites appeared to be altered in all brain regions examined except substantia nigra and dorsal amygdala, with maximal variation 2 or 3h after 3g ethanol administration. After repeated administration, the alterations following injections of 2.0g/kg were more marked than the injections of 1.0g/kg. Generally, the levels of NE, DA and 5-HT were decreased while the levels of HVA, DOPAC and 5-HIAA were increased with a few exception. The most prominent findings were seen in the striatum, nucleus accumbens and locus coeruleus. These data indicate that concentrations of monoamines and their metabolites can be determined simultaneously in discrete brain regions and that monoaminergic systems in the brain respond region-specifically to ethanol treatment.