In an effort to better understand the plasticity of tempered martensitic steels, uniaxial tension and compression tests were carried out. The temperature dependence of both the yield stress and the post-yield stress behavior were compared, and it was shown that a good correspondence exists between tensile and compressive behavior. The strain-hardening of EUROFER 97 steel was examined in terms of dislocation mechanics. A simple strain-hardening law was established within the framework of a model accounting for dislocation storage and annihilation. Moreover, an analytical constitutive equation was derived which describes the overall post-yield curve. While the equation predicts the flow stress should reach a saturation stress with strain, this Could not be verified by the mechanical tests due to deformation instabilities such as necking in tension or side-slip buckling in compression. Additional tests will have to be devised and applied to investigate these predictions. (C) 2002 Elsevier Science B.V. All rights reserved.