The activities of beta-glucosidases are stimulated by specific sulphur metabolites during the hydrolysis of complex polymeric organic carbon in an anaerobic sulphidogenic environment. While sulphate had little or no influence on enzyme activity, sulphite increased the activity of beta-glucosidases by 2.5 fold and sulphide increased the activity by six fold. A hypothetical model is proposed in which sulphur species (HSO3-and HS-), liberated at different times during the sulphate reduction process, activate the beta-glucosidases which are associated with the organic particulate matter leading to a subsequent enhancement of hydrolysis of polymeric carbohydrate material.