Plane strain compression tests of two V microalloyed steels and one plain C-Mn steel have been done to analyse the influence of the deformation temperature, in the warm working range, on the final microstructure and subsequent mechanical behaviour. In the case of V microalloyed steels, the reheating temperature has an effect on the amount of vanadium in solution prior to deformation. This factor influences the austenite evolution during warm deformation and the transformation during cooling. As a consequence, in the microalloyed steels complex multiphase microstructures are obtained that lead to a wide range of strength-toughness combinations. In contrast, in the case of the plain C-Mn steel minor effects are observed in the deformation range from 800 to 870 A degrees C.