the waste coming from cotton processing in mills in the textile industry is a lignocellulose-rich material, but has low digestibility, and is poor in proteins and minerals, making it inappropriate for ruminant feeding. this study was intended to evaluate the productivity and biologic efficiency of cotton textile mill waste in the production of the edible mushroom pleurotus sajor-caju, and to evaluate the alterations brought about in the waste for use in ruminant feeding. five treatments were undertaken in the following manner: t1- 80% eucalyptus sawdust + 20% wheat bran (control); t2- 50% waste + 50% sawdust; t3- 45% waste + 45% sawdust + 10% wheat bran; t4- 40% waste + 40% sawdust + 20% wheat bran and t5- 80% waste + 20% wheat bran. t5 showed the best results for productivity (22.46%) and biologic efficiency (71.48%). fungus altered the constitution of the substrates in the stages of production of the mushroom. therefore, the use of cotton textile mill waste in the cultivation of pleurotus sajor-caju may become a viable alternative for mushroom production, and also improve the quality of this waste for use in animal feeding.