A three-stage continuous culture system was used to segregate the component physiological groups of an anaerobic cellobiose-degrading association enriched and isolated from a landfill site. The optimum temperatures for methanogenesis were 30-35°C, although differences apparent in Vessels B and C at lower temperatures suggested the presence of distinct populations in the two vessels. There was no evidence of thermophilic methanogenic activity. Sulphate-reducing bacterial (SRB) activity was less affected by temperature perturbation, and there was significant SRB activity at 55°C.