An improved derivatization method for analysing 12 ring- and N-substituted amphetamine-derivatives in body fluids or seized materials by gas chromatograph combined either with mass spectrometer, electron capture or nitrogen phosphorus detector is presented. Heptafluorobutyric anhydride is used as derivatization reagent. No heating or standing period is needed in this procedure. Most of the drugs considered were distinguishable from each other according to their retention times and all of them according to their EI mass spectra. The base peak or one of the most intense peaks in the mass spectra contained benzyl radical and the m/e values were different according to the substituent.