The effects of modified water extractable pentosans (WEP) on gluten yield, dough properties, gluten quality and composition were studied. The results show that WEP interfere with gluten formation in both a direct and an indirect way. WEP interfere indirectly by competing for water and thus changing conditions for gluten development. This results in a lower gluten yield (GY) and an increased resistance of gluten against extension. The effect on GY can be corrected completely by adding more 0·2% NaCl solution during dough mixing. There is, however, also a direct effect of WEP on gluten formation. This effect is reflected in a lower extensibility of dough and gluten, that cannot be corrected by adding more 0·2% NaCl solution during dough mixing. It is demonstrated that the effect on extensibility of dough and gluten is related to the ferulic acid (FA) content of WEP. Also, addition of free FA leads to a more extensible dough and gluten together with a higher GY. We propose that WEP bound FA plays a key role in determining this effect of WEP. Our results also provide an indication that the effect of WEP on extensibility of dough and gluten may partly be due to cross-linking between protein and WEP.