The effects of vacuum carburizing under an acetylene atmosphere at 950 and 1000, followed by gas quenching and tempering at various temperatures on the properties of AISI S7 shock-resistant tool steel were studied. As carburized specimens undergo low temperature tempering, the surface hardness of the quenched specimens carburized at 1000 is lower than those of the specimens carburized at 950, due to the large amount of retained austenite in specimens carburized at 1000. Under high temperature tempering, specimens carburized at 1000 have higher surface hardness than specimens carburized at 950. As specimens are tempered in the range between 450 to 550, the surface hardness of carburized specimens show a modest increase due to the secondary hardening effects. According to the fracture toughness data, the toughness of carburized specimens peaked at tempering at 600.