The susceptibility of High Strength Low Alloy steels to Sulfide Stress Cracking (SSC) in H2S containing environments is evaluated by NACE TM0177-2005 test methods. Those SSC tests are commonly conducted at room temperature and atmospheric pressure. However because of the severity of some O&G wells there is a need for assessing the SSC susceptibility at higher partial pressures of H2S. The evolution of the SSC resistance of Sour Service grades (T95 and C110) with the H2S partial pressure has been investigated according to the uniaxial tensile (Method A) and double cantilever beam (Method D) corrosion tests in autoclaves. A general tendency of decreasing SSC resistance with increasing pressure is observed.