Centrifugal compressor applications require the use of martensitic stainless and martensitic precipitation hardening stainless steels at high hydrogen sulfide partial pressures. These materials do not perform well when tested with standard TM0177 test solutions. This paper describes the effect of hydrogen sulfide partial pressure, pH, and chloride content on their SSC resistance and explains their successful field operational experience. Environmental limits are determined for several materials and heat treat conditions. Keywords: sulfide stress cracking, SSC, stainless steel, martensitic, precipitation hardening, pH, chlorides