AbstractPost‐column derivatization of oligosaccharides after HPLC separation with a variety of systems has been achieved either by reaction with thymol in concentrated sulfuric acid or after hydrolysis of saccharides with hydrochloric acid and derivatization of the resulting monosaccharides withp‐aminobenzoic acid hydrazide. With both reactions the detection of reducing and non‐reducing sugars is possible even at trace levels. The latter reaction, despite the two reaction steps required, is much more convenient and practical, whereas with the first reaction it is also possible to determine alkylpolygluco