A detailed study of the strain-hardening on a Fe-9Cr-0.1C tempered martensitic model alloy has been undertaken in the temperature range of 77-343 K. The true stress-true strain curves were calculated from tensile test data. In the framework of a phenomenological model for the strain- hardening based on dislocation mechanics, it has been shown that, above 170 K, the whole post-yield behavior can be reasonably described by a single law. On the contrary, below 170 K, a careful examination of the strain-hardening indicated that the single law cannot describe anymore the entire post-yield strain range. It has been suggested that this behavior is related to the low mobility of the screw dislocations in the low temperature regime that influences the shape of the tensile curve. (C) 2004 Elsevier B.V. All rights reserved.