Extracellular manganese peroxidase (MnP) was purified from liquid cultures of the litter-decomposing basidiomycetes Agrocybe praecox and Stropharia coronilla. Both fungi produced MnP increasingly in response to Mn2+ in the Medium, A. praecox secreted two MnP isoforms with similar isoelectric points (pI) of 6.3-7.0 and a molecular weight (MW) of 42 kDa. MnP activity was not observed in Mn2+-free cultures of A. praecox. In Mn2+-supplemented cultures, S. coronilla produced at least two MnPs, of which the main isoform MnP1 has a pI of 6.3-7.1 and a MW of 41 kDa. In addition, S. coronilla possesses a partly, constitutive MnP (MnP2) which was also detectable in Mn2+-free cultures, although its amount was considerably lower. MnP2 showed two distinct bands with acidic p/s of 3.5 and 3.7 in the IEF gel and has a MW of 41 kDa. There are indications for the existence of a third, likewise Mn2+-inducible enzyme (MnP3), that could not be separated from MnP2 but formed an additional band in eletrophoretic analyses (pI 5,1, MW 43 kDa).