Xylan induced the production of xylanase by Verticillium dahliae. Other cellulolytic enzymes such as glucanase and beta-glucosidase were synthesized in smaller quantities. The process of degradation indicated that xylanase behaved like a typical endo-enzyme causing first production of high mol, wt. products, and indicated that V. dahliae produced at least three enzymes which degrade xylan.