Laccase and manganese-dependent peroxidase (Mn peroxidase) activities were detected in the culture media of Armillaria ostoyae and A. mellea. Mn peroxidase was produced in significantly higher quantity by the A. ostoyae isolates and was purified by chromatography from one isolate of this species. Some properties of the purified enzyme were examined (absorption spectrum, H2O2 and MnSO4 optimal concentrations, pH optimum and lactate stimulation). Enzymes of potential importance in the lignin degradation (especially Mn peroxidase) by Armillaria sp. are compared to those of other root-rotting fungi. The possible role of Mn peroxidase in modulating the pathogenicity of Armillaria sp. is discussed.