It is well known that specific xylanases have a positiv effect on dough and bread quality. The substrate for xylanases in wheat flour, arabinoxylan (AX) has been the subject for intensive studies over the last decade. Based on the results from these studies, it has been shown that solubilisation of water insoluble AX may influence dough and baking performance in a positive manner. From our work in this field we have a serie of xylanases with high homology, obtained by protein engineering. Despite their similar action on arabinoxylan, these xylanases differ in functionality. These xylanases have therefore been used as tools to characterise the newly reported xylanase inhibitor from wheat flour (Rouau and Surget, 1998). The inhibitor has been purified, using chromatographic techniques and characterised using SDS-PAGE, MS and amino acid sequence analysis. Furthermore, the inhibitor kinetics for the xylanases have been determined. The influence of the endogenous xylanase inhibitor on different xylanases, and thereby on the quality of dough and baked goods, will be discussed on the basis of biochemical, model experiment and baking trial data. Ref. Rouau, X.; Surget, A. (1998). Evidence for the presence of a pentosanase inhibitor in wheat flour. Journal of cereal science. 28: 63-70.