Metallurgical variables, mainly carbon distribution and the presence of nitrogen and metallic phases, can influence the corrosion behavior of austenitic, ferritic, duplex, and martensitic stainless steels. This article describes the effects of these metallurgical and processing variables on the susceptibility of the stainless steels to intergranular corrosion and intergranular stress-corrosion cracking and their testing methods. It explains the effect of sigma and related phases on the corrosion behavior of stainless steels.