The postweld heat treatment (PWHT) cracking susceptibility of standard and modified 2¼Cr-lMo and 3Cr-1 and 1½Mo steels has been investigated.The modified steels tested include three heats of 3Cr-1½Mo-0.1V, a heat of 3Cr-1½Mo-½Ni and a heat each of V-Ti-B modified 2¼Cr-1Mo and 3Cr-1Mo.Tests used to evaluate PWHT cracking susceptibility were Gleeble simulation and a C-Ring test adapted from that described in ASTM G-38 (used to evaluate stress corrosion cracking susceptibility).