Double-hit hot compression tests were carried on medium-carbon low-alloy steels using Gleeble 3800® thermomechanical simulator. The tests were performed at strain rates of 0.25 and 0.5 s-1 and temperatures of 1150 and 1200 °C with an interpass time of 5s. The onset of critical stress for dynamic transformation (DT) were detected using the double‐differentiation method. This metallurgical phenomenon was initiated under all testing conditions. The results show that the critical stress for DT increases with decrease in temperature and increase in strain rate.