The xylanase II (xyn2)- and endoglucanase I (egI)-encoding regions of Trichoderma reesei QM6a were successfully expressed in Aspergillus niger D15 under the transcriptional control of the glyceraldehyde-6-phosphate dehydrogenase (gpd) promoter from A. niger and the glaA terminator of Aspergillus awamori. A stable xyn2 transformant produced beta-xylanase activity of 8,000 nkat/ml and 5,000 nkat/ml in shake-flask cultures containing defined or 20% (v/v) molasses medium, respectively. The recombinant Xyn(2) enzyme expressed highest activity at pH 5-6 and 50-60 degreesC and retained more than 75% of its activity after 3 h of incubation at 50 degreesC. A stable egI transformant produced endo-beta-1,4-glucanase activity of 2,300 nkat/ml in shake-flask cultures containing defined media and about half the activity in 20% molasses medium. Maximum endoglucanase activity was obtained at pH 5 and 60 degreesC. Both Xyn2 and E-I retained >80% activity after incubation at 50 degreesC for 3 h. The heterologous Xyn2 and EgI represent a significant portion of the total extracellular proteins produced.