Many synthetic dyes present in industrial wastewaters are resistant to degradation by conventional treatments. Decolorization of four synthetic azo dyes was examined in two white rot fungal cultures. In solidified culture medium, Phanerochaete chrysosporium partially decolorized all the dyes tested, while Pleurotus sajorcaju totally decolorized amaranth, new coccine, and orange G, but not tartrazine. In liquid culture medium, P. chrysosporium totally decolorized amaranth, new coccine and orange G, and 60% tartrazine. Pleurotus sajorcaju totally decolorized amaranth and new coccine, 50% orange G and a maximum of 20% tartrazine. Neither fungus showed lignin peroxidase or veratryl alcohol oxidase activities, suggesting that these enzymes may not be involved in the decolorization. Manganese-peroxidase and beta -glucosidase may be involved in the decolorization of the dyes by P. chrysosporium, whereas in P. sajorcaju a laccase active toward o-dianisidine, and glucose-1-oxidase might participate in the process.