Concentrations of 3-methoxy-4-hydroxyphenylglycol (MHPG), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were measured in human lumbar cerebrospinal fluid following storage at room temperature and 4 degrees C for intervals up to 72 hours. These monoamine metabolites were quantitated using a high-performance liquid chromatographic-electrochemical detector technique. No significant difference could be detected in any of the three metabolites stored at room temperature for up to 48 hours. Addition of ascorbic acid to CSF had no measurable effect on the levels of HVA and 5-HIAA. Repeated thawing and freezing produced no detectable change in metabolite levels. The results indicate that these monoamine metabolites are stable at room temperature for up to 48 hours after lumbar puncture and that the addition of an antioxidant, such as ascorbic acid, is not necessary. The data also demonstrate that immediate refrigeration or freezing of samples is not required for maintenance of metabolite levels.