Trichoderma reesei LM-UC4 and Aspergillus niger ATCC 10864 were cultured as bio films on two different polyester cloths for cellulase production. Cellulase production was 40-50% higher in biofilm cultures inoculated with spores. Also, biofilm development and cellulase production were affected by the type of cloth used. Maximum cellulase activity of A. niger biofilm cultures (1.7 IU/ml) was 20% higher than that of T. reesei biofilms (1.4 IU/ml) and 140% higher than its correspondent freely suspended cultures (0.7 IU/ml).