Consortia of anaerobic bacteria were developed from different samples collected from various ecosystems for producing xylanases. We developed a promising thermophilic (KK-10) consortium producing cellulase-free xylanase (410 nkat ml(-1)) at 65-85 degrees C, pH 7-9, and mesophilic consortia PC-4, CC-2, and BD-2 exhibiting (580, 275, and 300 nkat ml(-1), respectively), elaborating xylanase with cellulases in the culture medium. The temperature and pH influenced the yield and pattern of xylanase and cellulase production markedly of the selected consortia, with the optimum at 72 h of growth growth and pH 6.7. The maximum xylanase activity was recorded for all the consortia at 37 degrees C except PC-3 and KK-10 consortia, which showed their highest activity at 55 degrees C and 65 degrees C, respectively. BD2 consortium when cultivated at 55 degrees C exhibited a several-fold increase in beta-glucosidase activity as compared with other consortia. It also had a broad pH range of 5-9 for the growth and xylanase production. A pH range between 6 and 7 was found optimum for other consortia. The maximum xylanase activity of 592 nkat ml(-1) was detected with PC-4 consortium. The xylanase of KK-10 could find industrial applications at higher temperatures, whereas neutral xylanases may be used in the food-processing industries.