Tandospirone has been reported as a serotonergic antianxiety drug with a different pharmacological mechanism from benzodiazepines. In the present study, the brain concentrations of monoamines and their metabolites were measured, comparing control rats and two groups of rats which were given tandospirone (10 mg/kg, ip) and diazepam (5 mg/kg, ip) each for 14 days. After sacrifice, brains of all animals were cut and divided into three portions, i.e. the cortex (COR), cerebellum (CER) and subcortical structures and brain stem (SS & BS). The concentrations of COR and SS & BS were measured using a Neurochemicalanalyzer (NCA, ESA, Inc., USA) with a reverse-phase column (Neurocolumn, Niko Bioscience Inc.). In the COR, 3-O-MDOPA (3-O-methyldopa) increased in the tandospirone group. In the SS & BS, 3-O-MDOPA increased in the diazepam and tandospirone groups. 5HIAA (5-hydroxyindoleacetic acid), DOPAC (3,4-dihydroxyphenylacetic acid) and HVA (homovanillic acid) decreased in the tandospirone group.