A rapid, sensitive and specific method for the analysis of the dihydroergotoxine alkaloids (dihydroergocornine, dihydroergocyrptine and dihydroergocristine) by gas chromatography and gas chromatography—mass spectrometry is described. The method is based on the quantitative thermal decomposition of the compounds in the injection port of the gas chromatograph, usign a 3% SE-30 column with a nitrogen detector. The sensitivity is about 1–10 ng. Gas chromatography—mass spectrometry was used for the structure elucidation of the thermal decomposition products of the dihydroergotoxine alkaloids and for the determination of these compounds at the picogram level.