Up to 200 mg 2,4,6-trinitrotoluene (TNT) l(-1) was removed within 12 h after adding it to a 5-day old culture of Irpex lacteus. The initial formation of hydroxylamino-dinitrotoluenes (2- and 4-OHAmDNT) from TNT was detected, followed by their successive transformation to aminodinitrotoluenes (2- and 4-AmDNT). Transformation of TNT to AmDNT via OHAmDNT was fast, but the next step was slow and seemed to be a rate-limiting step in TNT degradation. OHAmDNT isomers were also rapidly transformed by an in vitro enzymatic system. Both the mycelium and extracellular enzymes of I. lacteus were required for the TNT degradation.