A two stage approach based on modem control theory has been proposed to control the microstructure development during hot working. This method was utilized for optimal design of hot extrusion process. In the first stage, equations for dynamic recrystallization of plain carbon steel were utilized to obtain an optimal deformation path such that the grain size of the product would be 26 μm. In the second stage, the geometric mapping was utilized to develop an extrusion die profile such that the strain rate profile during extrusion matches with the optimal trajectory computed in the first stage. An extrusion experiment was performed to validate the proposed methodology, by utilizing the extrusion die geometry obtained in the second stage. The as-extruded grain size was observed to be in close agreement with the optimal design performed in the first stage. The results of the present investigation revealed that the principles of control theory can be reliably applied for the optimization and control of microstructure during deformation processing.