The use of liquid chromatography with on-line fluorescence detection has formed the basis for the separation, characterisation and quantitation of a number of metabolites of the psychotomimetic indolealkylamines N,N-dimethyltryptamine and 5-methoxy-N,N-dimethyltryptamine formed both in vitro and in vivo. Verification of the identity of metabolites has previously been facilitated by the combined use of a number of analytical techniques including multidimensional liquid chromatography and stop-flow spectroscopic analysis. We now describe the combination of liquid chromatography with gas chromatography-mass spectrometry for the unequivocal verification of a number of structurally characteristic metabolites of the psychotomimetic indolealkylamines.