Thermomechanical treatments basically aim at refining the grain size and controlling the crystallographic texture of metallic materials. First developed for the austenitic rolling of C±Mn steels, they are now being extended to a wide range of metals, e.g., aluminum, titanium, and nickel-based alloys. Dynamic or static recrystallizations are certainly the main mechanisms responsible for the microstructure and texture changes occurring during or after deformation. It is therefore not surprising that several teams of the Rhône-Alpes Federation are currently involved in parallel or converging investigations in that field. These researches take advantage of the availability of new experimental devices to produce large strains (Equal Channel Angular Extrusion, ECAE) and investigate the microstructures (orientation mapping by EBSD (Electron Backscattering Diffraction)), as well as the development of analytical modeling and numerical simulations. Some recent results are briefly summarized in this paper.Dynamic recrystallization (DRX), which occurs during straining, has long been considered to be restricted to low stacking fault energy materials, such as copper, c-iron, and the austenitic steels. In high stacking fault energy metals (aluminum, a-iron, ferritic steels), where the dislocation mobility is much larger, dynamic recovery was assumed to be the only operating mechanism. However, it is now well established that two types of DRX can take place: (i) discontinuous or ªclassicalº dynamic recrystallization (DDRX), occurring by nucleation and growth of new grains consuming rapidly the surrounding strain hardened matrix, and (ii) continuous dynamic recrystallization (CDRX) involving the generation of new grain boundaries by the progressive misorientation of neighboring subgrains.The main differences between DDRX and CDRX are the following: ± While the flow curves associated with DDRX switch from single to multiple peak behavior with increasing temperature and/or decreasing strain rate, such transition has never been observed for CDRX.± CDRX leads to strong crystallographic texture at large strains, whereas texture formation is hindered by DDRX. ± The temperature dependence of the flow stress (ªapparent activation energyº) is generally reported to be larger for DDRX, with some exceptions. Recent investigations involving large to very large strains imposed by torsion (i.e., monotonic simple shear) or ECAE (i.e., ªcrossedº simple shear) have shown that DDRX and CDRX combine the same elementary mechanisms, but with different kinetics. When grain boundary migration is slow, CDRX takes place; by contrast, in the case of large grain boundary velocity, the subgrain boundaries are swept by moving boundaries before they themselves transform into large angle grain boundaries. When DDRX takes place, the steady state microstructure is established quite rapidly (e<1). It displays strong heterogeneities, due to the coexistence of ªyoungº and ªoldº grains exhibiting low and high dislocation densities, respectively (Fig. 1). [1] CDRX is ...