A simple and reliable procedure for the simultaneous determination of dopamine (DA), serotonin (5-HT) and their acidic metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxy indoleacetic acid (5-HIAA) using high-performance liquid chromatography with electrochemical detection has been developed. Minimal sample preparation is required before injection into the liquid chromatograph. The present method can be applied to the analysis of several rat brain regions. The procedure offers good possibilities for routine analysis of biogenic amines and their acidic metabolites in the picogram range.