A mathematical model, for the prediction of the evolution of the microstructure during hot forming of microalloyed steels, is presented. The material behavior is combined with a finite-element model of the deformation. Multi-stage, isothermal compression tests are used for verification. The effect of the interruption between stages of compression on the restoration mechanisms is studied in three-stage tests. The influence of the deformation history on the microstuctural development and on the softening mechanisms is also analyzed. The distribution of austenite grain sizes is predicted. The inhomogeneity of the resulting structure is connected to that of the mechanical attributes of the deformed material. The studies show that additional grain refinement can be expected by controlling the recrystallization kinetics and the retained strain.