The treatment of dyeing processing textile plants effluents uses activated sludge system and can generate tons of sludges that needs to be appropriately disposed. Genotoxic compounds can be present in those sludges, especially from the class of the organics, that are difficult to be chemically analyzed in complex mixtures. The objective of this work was the evaluation of the genotoxic activity of sludge samples using the Salmonella microsome test, a bioassay very suitable for the screening of those substances in environmental samples. We analyzed 6 different textile dyeing facilities, that dyes both synthetic fibers (polyester, nylon and others) and cotton. The organic extractable material using methanol as solvent, varied from 0,24 to 6,7 por cento. From the 15 samples analyzed, 12 showed positive responses mainly with TA98 in the presence of metabolic activation (S9). Considering the type of the mutagenic response obtained, compounds such as azo dyes and or aromatic amines and others could be responsible for this activity. A chemical characterization of the genotoxic compounds present in those samples is very important in order to allow an adequate classification and disposal of this type of waste