Long term lab-scale and bench-scale experiments were performed to investigate the feasibility of the anaerobic process to treat wastewater from a pulp and viscose fibre industry. Anaerobic wastewater treatment enables an advantageous combination of COD, sulphate and zinc removal from viscose wastewater. The aim of the investigations was to evaluate the influence of the free sulphide concentration on COD and sulphate removal efficiency and on the substrate competition between sulphate reducing and methanogenic bacteria. Since the wastewater did not contain enough COD for complete sulphate removal it was of major interest to determine favourable process conditions to steer the substrate competition in favour of sulphate reduction. Further experiments at bench-scale permitted us to evaluate applicable COD-loading rates and gain fundamental information about process stability and optimization for large-scale implementation. The present work will deal with the most relevant experimental results achieved and with important technological aspects of anaerobic treatment of viscose wastewater.