A high-performance liquid chromatographic method for simultaneous determination of free catecholamines, their basic metabolites and serotonin in human urine was developed. The compounds were separated on a precolumn of cation-exchange resin and a mixed-mode (C18/cation-exchange) column and determined by an eight-channel electrochemical detector. By this method, free norepinephrine (NE), epinephrine (E), dopamine (DA), normetanephrine (NMN), metanephrine (MN), 3-methoxy-tyramine (3-MT) and serotonin (5-HT) were determined in 40 min with inter-assay precision of 1.9, 3.2, 1.2, 1.6, 1.6, 5.5 and 3.2%, respectively. Detection limits were between 0.05 (E) and 0.3 (3-MT) pmol. The mean values of analytical recovery for NE, E, DA, NMN, MN, 3-MT, 5-HT were 99, 104, 104, 99, 102, 109 and 99%, respectively.