Mass spectra of the trifluoroacetyl esters of the trichothecenes deoxynivalenol, diacetoxyscirpenol and T-2 toxin, as well as zearalenone, were obtained by gas chromatography-electron ionization mass spectrometry. Quantitation of deoxynivalenol as its trifluoroacetyl ester by selected ion monitoring was then possible down to 10 pg in the mass spectrometer (equivalent to 1 ng/g in a sample). The method was tested by extracting and analysing mouldy wheat which had previously given a positive result for deoxynivalenol when analysed by thin layer chromatography. The method was also suitable for the analysis of diacetoxyscirpenol and T-2 toxin; however, quantitation of zearalenone was unsuccessful because of the instability of the derivative.