1. A simple HPLC method using sodium dodecyl sulfate (SDS) and electrochemical detection for the determination of norepinephrine (NE), 5-hydroxytyramine (DA) and 5-hydroxytryptamine (5-HT) in brain regions is described. 2. The tissue extraction procedure involved only two steps: protein precipitation with perchloric acid and pH adjustment to near 3.0. When used in combination with methanol as ion-pair in the mobile phase, sodium dodecyl sulfate effectively separated NE (6.6 min), epinephrine (EPI, 7.9 min), DA (14.3 min) and 5-HT (29.0 min) and the high methanol concentration used prevented the overlapping of the metabolites and monoamines in their chromatographic peaks. 3. The method was sensitive (40 to 70 pg of monoamine can be quantified) and reproducible and the values obtained for cortex, hippocampus, striatum and substantia nigra were consonant with most literature data.