A series of binary nickel-beryllium alloys, ranging in content from 0.0036 to 0.30 wt.-% Be, has been internally oxidized isothermally at temperatures in the range 1000–1350°C (1273–1623 K). The kinetics of subscale formation has been followed metallographically. Although fine dispersions of BeO were formed upon internal oxidation of the more dilute alloys, their volume fraction was inadequate to produce significant hardening. The kinetic data, together with some hitherto unpublished results of Seebohm, have been analysed, and indicate a value of 4.29 ± 0.23 eVfor the activation energy for the diffusion of oxygen in nickel over the temperature range considered. The value of Do for the process was found to be 3.10 × 102 m2/s.