300 series stainless steel foils containing stress corrosion cracks (SCC) grown in high temperature aqueous environments have been examined by TEM. Crack tips are oxidized and havea three-layered morphology where all the layers taper towards the crack tip. The inner layer is a microcrystalline spinel sandwiched between outer layers of a nanocrystalline oxide. The outer layers are enriched in Cr, and the inner with Fe, relative to the matrix. Cu was observed to segregate at the interface between oxide and matrix at one crack in type 316 steel.