The upgrading of sugar cane bagasse with natural rubber waste by irradiation and three mushroom fungi was studied in order to produce economical animal feed and mushrooms. The protein concentrations changed a little at 0, 1% of NRSP but greatly increased at 5% NRSP concentration with irradiation and nonirradiation in liquid fermentation. The filtration rate decreased at 5% NRSP concentration after liquid fermentation but it increased by 2.7, 10.2, 11.1 times with irradiation for P. sajor-caju, C. phlytidosprorus and P. flavellatus. The amounts of crude fiber were decreased due to the irradiation and the different concentration of NRSP after 42 days of solid fermentation by P. sajor-caju. (C) 1998 Elsevier Science Ltd. All rights reserved.