Textile wastes can be difficult to treat and it is not uncommon for dye residues to impart colour and ''hard'' COD to the treated effluent. This paper examines the use of a sequence of biological filters; anaerobic followed by aerobic; to treat a simulated textile waste. Two dyes were used in its formulation, Add Yellow 17 and Basic Red. Acid Yellow (25 mgl(-1)) was not removed by the sequence of fillers and subsequent batch tests showed that it was not sorbed onto the biomass. The anaerobic filter converted some 80% of the incoming COD (2000 mgl(-1)) to volatile fatty acids and the overall process removed > 92% of the COD and > 99% of the Basic Red (200 mgl(-1)). The capability of the anaerobic filter to withstand shock loads was also examined. Of these, only the high flow rates associated with the hydraulic shock caused serious disruption to the operation of the process.