Carbon steel plates employed in welded pressure vessels may be susceptible to one or more forms of environmental cracking when exposed to wet H2S service conditions. One of these is called stress-oriented hydrogen induced cracking (SOHIC).Cracking observed in steel equipment resulting from SOHIC appears to be mechanistically related to HIC because it involves the formation of small blisters in the steel and the development of interconnecting cracks that link adjacent blisters on different planes in the steel, however, in SOHIC, the orientation of these blisters is much different. The presence of an applied or residual tensile stress in the steel (typically adjacent to the weld heat-affected zone) produces stacked arrays of these blisters and the interconnecting cracking is oriented in the through-thickness direction. Susceptibility to HIC has been generally shown to be gratest in high-sulfur steels and decrease with decreasing sulfur content of the steel. By comparison, in severe hydrogen-charging environments, SOHIC susceptibility can increase as the sulfur content in the steel decreases from the level commonly found in the conventional plate steels until very low levels of sulfur are reached, when susceptibility to SOHIC can decrease. However, at very low sulfur contents, several other variables in the steel may play a role in determining SOHIC as well. These include the presence of ferrite-pearlite banding, carbide phase hardness, calcium treatment, and inclusion morphology, among others.