With the aid of an ASC-type finishing line (Automatic System Control) and continuous cooling of the rolled stock in water boxes, modern continuous light mills enable thermomechanical (controlled) rolling of SBQ-type rods (Special Bar Quality). During the thermomechanical forming (at different temperatures or cooling rates etc.), one can analyze the quality parameters of roundsection steel bars. In order to obtain better understanding to the forming conditions (temperature, strain and strain rate) and the possibility of cooling (related to its rate and time), an experiment involving continuous and discontinuous testing by means of a Gleeble plastometer was suggested. After its implementation, the attention was focused on the mathematical interpretation of the stressstrain characteristics of the steel and on metallographic observation of microstructural changes. The results achieved are of universal meaning and contribute to the theoretical understanding of controlled forming.