The concentration of endogenously formed tryptamine in central nervous system tissue was determined after extraction into ethyl acetate, purification on a weak cation-exchange resin and analysis using high-performance liquid chromatography with fluorometric detection. Final chromatographic separation of this indoleamine was achieved using a muBondapak C18 reversed-phase column under isocratic conditions. Using this method, the concentration of tryptamine in the whole brain of normal rats was found to be 0.60 +/- 0.06 ng/g of tissue, while pretreatment with dl-p-chlorophenylalanine, tranylcypromine and l-tryptophan increased the concentration to 96.7 +/- 21.9 ng/g.