The culture supernatant of Thermomyces lanuginosus strains MED 2D and MED 4B1 had high activities of xylanase with low inducible activities of beta-xylosidase. The crude xylanase was optimally active at 70 degrees C and at pH 6.0 to 6.5. Subsequently Eucalyptus kraft pulp was treated with MED 2D supernatant at 10 IU per gram pulp resulting in a 10.5% reduction in Kappa number. XECEDED-Refined bleached pulp resulted in handsheets with increased brightness compared to the control (X = xylanase treatment; E = alkaline extraction; C = Cl-2 treatment; D = ClO2 treatment).