Trichoderma reesei QM 9414 was cultured to produce cellulase and biomass using as substrates untreated bagasse (non-alkali-treated bagasse washed with distilled water), and bagasse alkali-treated at room temperature and at 100 degrees C, washed with water at pH 2. Avicel (microcrystalline cellulose) was used as a control substrate. When untreated bagasse and bagasse alkali-treated at room temperature were used, appreciable cellulase activity was found (0.085 and 0.090 IU/ml, respectively), but activity was lower than when Avicel was used (0.163 IU/ml). Enzyme yields were 16, 19 and 22 IU/g cellulose consumed, respectively. Cellulase activity was not detected when bagasse alkali-treated at 100 degrees C was used. The biomass yield was about 30% lower when bagasse was used as a substrate than when Avicel was used. The yield was higher wizen bagasse was alkali-treated than when untreated bagasse was used although the difference was small. The biomass yield was 0.78 g biomass per g cellulose consumed for alkali-treated bagasse at room temperature versus 0.50 g/g for bagasse alkali-treated at 100 degrees C, 0.57 g/g for untreated bagasse and 0.67 g/g for Avicel. It was concluded that untreated bagasse is as good a substrate for cellulase and biomass production as bagasse alkali-treated at room temperature. Copyright (C) 1996 Elsevier Science Ltd.