The aim of the present work is to develop the hardenability and tempering models for various quenching and tempering treatments of high strength/martensitic steels. The hardenability model is divided in three sub-models: 1. Dissolution of particles during reheating. 2. Kinetic calculation of hardenability with respect to dissolution of particles. 3. Grain size and grain growth is considered in relation to particles and their dissolution. The hardenability model can be used specifically for steels containing less than 0.4% C. For C-contents below 0.2%, Cr and Mo has less influence on hardenability, while there is a positive interaction effect between Mo and Ni. This is considered in the modelling. The semi-empirical tempering model is combined with the hardenability model for prediction of hardness and ultimate tensile strength at room temperature after tempering. The final properties are dependent on dissolution of alloying elements during reheating. Predicted properties for different steel grades by hardening and tempering models were compared with hardness and tensile strength results determined experimentally. The models are verified with examples of experimental data of hardened and tempered high strength steels. The tempering model generally works well in comparison with experimental data. The pre-history treatment of steel before quench affects the level of hardness and strength after tempering which is considered in the modelling.