Purpose: The main purpose of this paper was to estimate the effect of the dynamic conditions resulting from deformation process on the austenite decomposition into ferrite and pearlite (A->F+P) in the commercial carbon steel. Design/methodology/approach: In the paper flow stress curves and microstructure of deformed steel within the range of discontinuous (austenite to pearlite) and austenite to ferrite transformation at different strain rates and cooling rates were presented. The microstructure of hot deformed samples was tested by means of an optical and electron microscopy. Findings: It was shown that the flow localization during hot deformation and preferred growth of the pearlite colonies at shear bands was very limited. The most characteristic feature of the microstructure observed for hot deformed samples was the development of carbides that nucleated along elongated ferrite grains. Research limitations/implications: In spite of intense strain hardening due to deformation and phase transformation overlapping, microstructural observation of deformed samples did not reveal significant flow localization effects or heterogeneous distribution of the eutectoid components. Therefore complementary tests should be carried out on the steel with higher strain above the 0.5 value. Originality/value: There was no data referred to particular features of the dynamic processes, such as dynamic recrystallization and recovery, dynamic precipitation, that can occur during austenite decomposition into ferrite, and especially during discontinuous transformation of austenite to pearlite.