Anaerobic treatment systems have been successfully applied over the last decade for combating wastewater pollution loads in the forest industry. However, anaerobic treatment of certain paper mill waste streams is limited by the presence of toxic and recalcitrant organic compounds, high concentrations of sulfur and in some cases high wastewater temperatures. Nonetheless, the future perspectives for the anaerobic treatment of difficult forest industry wastewaters are encouraging. This paper discusses a variety of measures available to anaerobic treatment technologies for dealing with the aforementioned limitations.