The partitioning of Mn in the multiphase structure of a low-alloy 04G4 steel, showing a transformation-induced plasticity effect, was investigated using transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDS). The application of a soft annealing at 898 K for 1-60 h between hot rolling and cold rolling activates Mn diffusion in the ferrite matrix and Mn enrichment processes in the cementite. During continuous annealing at 973 K in the (alpha + gamma) temperature range new austenite (gamma) is formed. A non-uniform distribution of Mn between bainitic and polygonal ferrite (alpha) matrix and retained austenite was observed after accelerated cooling. An increase of Mn content up to 10 wt.% was detected in proeutectoid cementite and in martensite-austenite islands after water quenching from 973 K. (C) 2003 Elsevier Science B.V All rights reserved.