Our just received results on the deformation microstructures evolved in a medium-Mn austenitic steel during large strain warm to hot rolling were analyzed with a reference to other alloys with face centred cubic lattices and relatively low stacking fault energies. The structural changes were characterized by the development of dynamic recovery (DRV) and dynamic recrystallization (DRX). The deformation grain size decreased while the dislocation density increased with a decrease in deformation temperature. Both the grain size and the dislocation density could be expressed by power law functions of temperature-compensated strain rate, i.e., Zener-Hollomon parameter, with exponents of -0.33 and 0.2, respectively, in the case of discontinuous DRX. On the other hand, the exponents of -0.1 and 0.06 were obtained for the grain size and dislocation density dependencies on the temperature-compensated strain rate, respectively, under conditions of warm deformation accompanied by DRV and continuous DRX. Therefore, a power law function could be obtained between the grain size and the dislocation density with a grain size exponent of -0.6, irrespective of the mechanisms of microstructure evolution in a wide range of deformation conditions.