The maximum yield of cellulases from Aspergillus terreus GTC826 grown at 40-degrees-C on water hyacinth was after 120 h in a medium containing 0.5% (w/v) water hyacinth, 0.25% (w/v) NH4NO3 and 0.4% (w/v) Tween 20 with an initial pH 6.0. Aspergillus terreus produced two to three times more beta-glucosidase activity (assayed at 60-degrees-C) than Trichoderma reesei QM9414 grown on the same substrate at 28-degrees-C but assayed at 50-degrees-C.