The thermal properties, the Rockwell hardness (HRC) and the microstructure of three end-quench bar (Jominy bar) steels (C48, 42CrMo4 and 35NiCrMo16) have been investigated. The thermal properties are determined using photothermal deflection (PTD) technique and the hardness is measured by the Rockwell durometer. In this paper we have tried to relate the thermal properties to the hardness for each steel illustrated by an empiric mathematical equation. (C) 2008 Elsevier B.V. All rights reserved.