The concentrations of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), 4-hydroxy-3-methoxyphenylglycol (HMPG), and glutamate were determined in cerebrospinal fluid (CSF) and serum in 10 healthy volunteers. The monoamine metabolites were measured by mass fragmentography and the glutamate by high-performance liquid chromatography. The level of glutamate in CSF was low (0.34 +/- 0.14 nmol/ml) in comparison with previously published values. The concentrations of monoamine metabolites in CSF were in close agreement with earlier findings. There were negative correlations between the concentrations of HVA (r = -0.82, p less than 0.01) and 5-HIAA (r = -0.77, p less than 0.01) and glutamate in CSF, but not in serum. The serum levels of HMPG and glutamate were negatively correlated (r = -0.95, p less than 0.001), but not the CSF levels. The HMPG levels in serum and CSF were positively correlated (r = 0.94, p less than 0.001), but not the HVA and the 5-HIAA levels. The serum and CSF levels of glutamate were positively correlated (r = 0.67, p less than 0.05). The results indicate relationships among the metabolism of dopamine, serotonin, and glutamate in the brain and between the metabolism of noradrenaline and glutamate in peripheral tissue.