Kraft and soda delignification kinetics of wheat straw,Triticum aestivum, have been studied as a function of OH “concentration, HS” concentration, and temperature. It was found that about 90% of the lignin is dissolved in the rapid initial phase. The rates of delignification in the bulk and residual phases were found to be similar to those of birch wood,Betula pubescens.The amount of residual phase lignin was found to be considerably less than in birch or spruce,Picea abies, and it was affected by the same factors, A model that accurately describes the delignification of wheat straw was derived.