Three concentrations (0.1 mM, 0.5 mM, and 1.0 mM) of sodium molybdate were added to continuously fed anaerobic upflow filters (1.01) treating a high-sulphate molasses wastewater which contained approximately 27.0 g chemical oxygen demand/1 and 6.0 g sulphate/1. Sodium molybdate (0.1 mM) did not inhibit sulphate reduction by the filter. Higher concentrations (0.5 mM and 1.0 mM) inhibited sulphate reduction but metanogenesis was also slightly affected. The microflora of the filters adapted to the continuous presence of sodium molybdate (1.0 mM) and sulphate reduction was then evident. Addition of a higher concentration of sodium molybdate was then necessary to inhibit sulphate reduction but methanogensis was also adversely affected.