Transformation plasticity (TP) may cause distortion of steel work-pieces during production processes like heat treatment, for example. Recent results show, that there are effects in the material behaviour which cannot be described by models widely used today. For instance, a varying load during the transformation may lead to a backstress effect which is not predicted by the well-known Franitza–Mitter–Leblond TP model. The extended TP model presented here consists of a back stress due to TP itself, i.e., generated by the TP strain. The authors continue their investigations (e.g., at the IWCMM14 in Goa [M. Wolff, M. Böhm, M. Dalgic, G. Löwisch, N. Lysenko, J. Rath, Comput. Mater. Sci. 37 (1–2) (2006) 37–41], at the IDE2005 in Bremen [M. Wolff, M. Böhm, M. Dalgic, G. Löwisch, J. Rath, in: H.-W. Zoch, T. Lübben (Eds.), Proceedings of the 1st International Conference on Distortion Engineering, September 2005, Verlag Universität Bremen, Bremen, Germany, 2005, pp. 14–16]) of the pearlitic transformation of the steel 100Cr6 under step-wise loads and validate some proposals for TP.