Extracellular manganese peroxidase (MnP) was purified from the compost extract of Agaricus bisporus using anion exchange chromatography, gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Two forms (MnP1 and MnP2) were separated by isoelectric focusing and their isoelectric points were determined to be 3.25 (MnP1) and 3.3 (MnP2). Both forms had a molecular mass of 40 kDa. The first 25 amino acids of the N-terminal end of MnP1 sequence was found to share 68% identity with a Pleurotus ostreatus and a P. eryngii MnP. Lignin peroxidase was not detected during any of the steps in the purification process. In liquid cultures with both soluble and insoluble carbon sources in defined medium (D-glucose? glycerol, Whatman CC-41 microcrystalline cellulose or Solka-floc cellulose) MnP protein was detected in culture fluid by Western blot, but no MnP activity could be detected. A. bisporus appears to be in the group of ligninolytic fungi which do not produce lignin peroxidase.