The manufacturing process of olive oil yields a liquid waste called ＇olive mill wastewater＇ (OMW). This waste has a high polluting power as well as a high antibacterial activity exerted, among others, by various phenolic compounds. Among the methods for the purification of OMW, biological systems show some advantages that make these particularly suitable. However, the presence of phenolic inhibitors requires the use of microorganisms able to utilise aromatic compounds. The capability and kinetic behaviour of several fungi to deal with such a waste reducing the phenol content of OMW was studied. The removal of total phenols relative to the total organic load consumed, which might indicate a measure of the selectivity with which the microorganisms remove phenols among other organic compounds present, indicates the sequence: Phanerochaete chrysosporium > Aspergillus niger > Aspergillus terreus. (C) 2000 Elsevier Science Ltd. All rights reserved.