Microstructure has a strong influence on hydrogen absorption thus sulfide stress cracking (SSC) resistance of high strength steels. A recently developed 125 ksi grade casing material demonstrated good SSC resistance in mild sour environment. However the relationship between the material’s microstructure and its SSC resistance is still not well understood.In this investigation a proprietary 125 ksi grade casing material with different wall thickness yield strength and hardness were selected. The hydrogen absorption characteristics of the 125 ksi grad casing material have been evaluated by thermal desorption spectroscopy (TDS) and hydrogen permeation tests. The internal strain of the materials after tempering was measured using X-ray diffraction technique. The microstructure factors of the material such as pre-austenite grain size precipitate shape size and distribution were determined using electron backscattered diffraction (EBSD) technique and transmission electron microscope (TEM) respectively. Correlations are established between grain size dislocation density precipitates size and diffusible hydrogen and total absorbed hydrogen. Furthermore these relationships were used to explain the SSC resistance of the materials.Keywords: sulfide stress cracking thermal desorption spectroscopy transmission electron microscope electron backscattered diffraction X-ray Diffraction Fang Cao1 Weiji Huang2 Cecilie Haarseth2 Russ Mueller1 Ning Ma1 and Srinivassan Rajagopalan11ExxonMobil Research and Engineering Company Clinton NJ2ExxonMobil Development Company Houston TX