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Abstract. The use of the combined influence of retained austenite and bainitic ferrite to improve strength and ductility has been known for many years from the treatment of multiphase steels. Recently, the very fine films of retained austenite along the martensitic laths have also become the centre of attention. This treatment is called the Q-P process (quenching and partitioning). In this experimental program the quenching temperature and the isothermal holding temperature for diffusion carbon distribution for three advanced high strength steels with carbon content of 0.43 % was examined. The alloying strategies have a different content of manganese and silicon, which leads to various martensite start and finish temperatures. The model treatment was carried out using a thermomechanical simulator. Tested regimes resulted in a tensile strength of over 2000MPa with a ductility of above 14 %. The increase of the partitioning temperature influenced the intensity of martensite tempering and caused the decrease of tensile strength by 400MPa down to 1600MPa and at the same time more than 10 % growth of ductility occurred, increasing it to more than 20%.