Gas-liquid chromatography (GLC) of trifluoroacetylated (TFA) whole cell methanolysates as a procedure for obtaining species specific GLC elution profiles has been introduced. This method and a modification of the previously described trimethylsilyl (TMS) derivatization used for identical purpose were tested on four strains belonging to the bacterial species Neisseria catarrhalis, N. ovis and N. meningitidis. The TFA and TMS elution profiles are compared, and their usefulness in characterization of strains and species in relation to the best reproducibility obtainable is discussed. The TFA method gives better resolved and more reproducible elution profiles. The method appears to have a high potential as an aid in bacterial classification and identification.