the thermophilic fungus sporotrichum cellulophilum was immobilized with nonwoven materials for cellulase production. the concentration in the medium was an important factor controlling cellulase production. the growth of the immobilized fungi depended on the spaces in the nonwoven materials. immobilized growing fungi were retained by the nonwoven materials, and the supernatant medium did not contain mycelia. the heat stability of the immobilized growing fungus was higher than that of the free fungus. the immobilized fungus gave the same fpa as the free mycelium, but the lag time for cellulase production in the immobilized fungus was longer. it was necessary for the only medium to be changed in order to get the immobilized growing fungus to continue producing cellulase. there was no difference of lag time with the free cells, and the supply of cellulose powder and polypepton was reduced to two-thirds. after 23 exchanges of the medium (2. 6 mg cellulose powder/1 cm**3 nonwoven materials) fpa value was maintained. the periodic batch culture was continued for 69 days. (edited author abstract) 12 refs