A gas chromatographic procedure with flame ionisation detection has been developed to measure 2-phenylethylamine in human urine as the trifluoroacetyl derivative. The amine is purified by an ether extraction procedure and derivatised with trifluoroacetic anhydride. Quantification is obtained by comparing the peak height with that for an internal standard added to the urine before extraction. The normal 24-h excretion value for 2-phenylethylamine in human urine is found to be 6.8 +/- 2.9 mug (mean +/- S.D.).