Cellulase production by Aspergillus niger was compared in three different culture systems: biofilm, solid-state, and submerged fermentation. Biofilm and solid-state fermentations were carried out on perlite as inert support, and lactose was used as a carbon source in the three culture systems. In cryo-scanning electron microscopy, biofilm and solid-state cultures gave similar morphological patterns and confirmed that both spore first attachment and hyphal adhered growth are helped by the production of an adhesive extracellular matrix. Biofilm cultures produced higher cellulase activities than those in submerged and solid-state cultures (1,768, 1,165, and 1,174 U l(-1), respectively). Although biofilm cultures grew less than the other cultures, they produced significantly higher cellulase yields (370, 212, and 217 U g(-1) lactose, respectively) and volumetric productivities (24, 16, and 16 U l(-1) h(-1), respectively). Likewise, endoglucanase and xylanase activities were higher in biofilm cultures. Under the conditions tested, it seems that fungal attached growth on perlite may favor better enzyme production. Biofilms are efficient systems for cellulase production and may replace solid-state fermentation. Biofilm fermentation holds promise for further optimization and development. The results of this work reveal that fungal biofilms may be used for the commercial production of cellulase employing the technology developed for submerged fermentation at high cell densities.