The austenite grain growth kinetics of 1045, 4140, 52100 steels have been experimentally determined at 850, 900 and 950°C. The kinetics has been analyzed using standard diffusional models as well as grain pinning effects. In addition, the effects of austenite grain size and starting temperature on the hardenability of 1045 has been determined by Jominy End-Quench tests.