A gas chromatographic-mass spectrometric method is described for the analysis of I-methyl1,2,3,4-tetrahydro-beta-carboline in alcoholic beverages. The analytical procedure involves the addition of semicarbazide and a deuterated analogue as the internal standard, followed by extraction with toluene-isoamyl alcohol and derivatization with pentafluoropropionic anhydride. Multiple ion detection showed 1-methyl-1,2,3,4-tetrahydro-beta-carboline to be present in alcoholic beverages prepared by fermentation processes. The range of concentrations was 4.8 - 450 nmol/litre in wine and 9.1 - 69 nmol/litre in beer.