Improving the hot strip mill process is mandatory for the steel industry owing to the increasingly severe specifications being imposed by end users. Within this objective the development of a metallurgical model that links the operating variables in the mill with microstructure and mechanical properties of the final products becomes of great importance. This model could provide useful information for process control and optimization, reducing the need of costly on-line experimentation. In this thesis, some previously published experimental and theoretical studies of hot rolling are reviewed. The aim of this work is to present a metallurgical model that could describe the microstructural evolution of C-Mn steels during hot rolling. During hot deformation the average dislocation density of the material increases several orders of magnitude. Two metallurgical processes become active to reduce the dislocation excess: recovery and recrystallization. In austenite, the later is the most important restoration process. Depending on temperature, strain and strain rate the recrystallization could begin during deformation (dynamic recrystallization) or in the interpass time (static recrystallization). In order to describe the microstructural evolution it is needed a description of the recrystallization progress and the resulting austenite grain size after each reduction step in the rolling mill. In addition further modifications of the grain size could take place if the recrystallization after deformation is complete and is followed by grain growth. After hot deformation the austenite transforms to ferrite, perlite and/or bainite. The transformation kinetic and final phase distribution depend strongly on the austenite microstructure (grain size and accumulated strain), and on the cooling and coiling conditions. Due to the important metallurgical differences between the several phases that may appear, it is needed an accurate description of the final microstructure in order to evaluate the mechanical properties of the material. The present work combines the use of models developed from hot torsion test data and from the analysis of industrial mill logs. Logged data were collected from the Mobarakeh Steel Complex (MSC) nine-stand (thirteen-pass) HSM. For each strip, the following data were used: chemical composition, strip width, strip thicknesses before and after all passes, work roll rotational speeds, roll forces, interpass times, and temperatures (mean values) for each pass. The previous parameters were then employed to calculate the true strains, strain rates, and MFSs, according to the Sims formulation, roll flattening, redundant strain, and forward slip between roll and strip and were organized using MATLAB software. An MFS model was developed to predict the strip-rolling behaviors of plain C-Mn. It is based on an improved Misaka MFS equation and takes into account the quantities of the important alloying elements, the extent of recrystallization between passes, strain accumulation, and the possibility that DRX is initiated during a given pass. A metallurgical algorithm that comprises the prediction of the microstructural evolution during hot rolling (austenitic range) and the subsequent phase transformation was developed for C-Mn steels Keywords: Mean flow stress (MFS), Recovery, Static recrystallization, Dynamic recrystallization, Grain size, Hot torsion test, Microstructural evolution during hot rolling