Compatibility tests were carried out with various types of stainless steel and fission product doped overstoichiometric UO 2 to investigate the influence of cladding material composition and preliminary treatment on the corrosion. Tensile tests on the corroded steel specimens should give an indication how the mechanical properties of a pin cladding are affected by the chemical interactions with the fuel. The results showed that the depth of corrosion depends essentially on the steel composition; the influence of pretreatment is of secondary importance. Mechanical properties are effected by corrosion to a various degree depending mainly on the composition of the steels. A comparison of reduction in rupture strength and visible zones of attack gave an indication of the relevance of measured penetration depth for an assessment of the load capacity of a fuel cladding after corrosion.