Kinetic studies on the oxidation of nickel using the vacuum microbalance method have been extended to 1050°C in order to determine the conditions and mechanisms of breakdown of the metal in oxidation. Below 900°C Ni oxidizes in the normal manner and the rate data fit in well with experimental rate relationship already established. At 900°C and higher, parabolic rate law plots of the data show increasing values of the constant with time. At 1000°C and higher, the oxide cracks away from the metal. It is suggested that Ni fails in protective oxidation due to a loss of adhesion at the oxide metal interface.