Tetramethylpyrazine (TMP), an active ingredient in Chuanxiong (Ligusticum Wallich Franch), a traditional Chinese herb, has been widely used especially in the treatment of patients with cerebral ischemic diseases in China. TMP was reported to have a short half-life time because of its rapid metabolism in the liver. In this paper we studied its metabolites in human urine with GC/MS after oral administration of TMP. Three metabolites were found in the water soluble acidic fraction of the urine and the main metabolite was identified to be 3,.5,6-trimethylpyrazinecarboxylic acid.